Yeah, with no concentration, no chance for a save at will as many times a day as you want to do it. It is very powerful in play
Can't agree with that. First of all, you're a sitting duck and most likely get slaughtered. Second of all, with those actions, you could cast a control spell like Wall of Force, drop a Greater Demon behind the enemies, control a group of enemies with Hypnotic Pattern, debuff an entire group with Synaptic Static, just kill that guy, or do a lot of other things that have a much bigger impact.
Split Enchantment is not a free upcast It targets two creatues. On some spells that is an upcast, on most, including the better ones, it is not. Dominate Person//Monster, R. Psychic Lance, Ottos Dance, Power Word Stun, Power Word Kill, Befudlement, Suggestion, Dissonant Whispers. You can target two creatures with all of these but you don't do that on an upcast. Moreover you can do it over and over again in a single day. Take a look at the spells above; I could use it with almost all of them in the SAME day and use it on most of them multiple times that day.
Finally on the spells it is an upcast, being able to target two creatures without upcasting is a big deal when you are talking about higher level spells. I can cast a 5th level hold monster and target 2 creatures, and while that is not as good as the examples above, that is still a heck of a bargain compared to a 6th level spell to do the same thing.
But tell me, you and your buddies are level 12 and you're fighting a Death Knight CR 17 in a deadly encounter. How are you going use the Enchantment Wizard's features to help your party get out ahead? Or you're playing Eve of Ruin and are 17th level and all that stands between you and the next part of the Rod of Seven Pieces is the CR 23 Tiefling Bard Windfall. How are these features going to help you win the fight? Because those are the fights where it matters. One has Magic Resistance and a Wisdom save of +9, the other immunity to the charmed condition; and there's only one target. Looks to me like they're just a base class Wizard now. Selune's Viper would also only work against Windfall, due to the Immunity to the Poisoned Condition of the Death Knight, but she has an Initiative of +14 and can hit everything within 30 feet with her bonus action for a DC 23 Con save and a stun upon fail.
And those aren't outliers because high Wisdom saves and immunity to charmed are quite frequent at higher levels and then you often have legendary resistances on top at least for the boss fights.
I would say Arcane Abeyance is generally less powerful in play.
It's generally considered the most powerful feature in the game by the likes of D4, Treantmonk, Dungeon Dudes, Pack Tactics, and others. But you don't have to agree with that.
There are some cases where a party designed to leverage it would be better, and it offers some flexibility that is situationally powerful (the cleric has burned through a lot of slots with healing but you haven't. It is limited uses, limited duration, you are still using the slot, the player casting it is still using their action and that really limits the ceiling for this ability.
You can give it to your familiar and let them cast it.
If you use a low level spell, the player yyou give it to probably has a better action. If you use a high level spell you give up the ability to use that slot on a different spell better for the situation and take the risk of losing it completely.
It effectively lets you have an additional 4th level spell active at the same time without being limited to a particular school of magic. I know, I said 5th level spell previously and I apologize for the error. I confused myself by not having my glasses on. So, Summon Dragon is out, but it still allows a Battlemaster Fighter to have Summon Minor Elementals active, if they're interested in that. Or have the familiar or whomever concentrate on Summon Aberration or the like.
Arcane Abeyance, is most powerful when you know exactly what high level spell you will need to use ahead of time and you know that will happen in an hour. I just don't find that this happens very often
I can't tell why. Since using Arcane Abeyance takes the casting time of the spell, hence in most cases an action, you can do it right before combat. If you used your Wizard spells wisely and scouted ahead with Arcane Eye, Scrying, and other divination spells, you know what's coming, unless your party doesn't do that sort of thing. But if you know what's coming, you can use the Study Action and find out what these enemies are about and maybe learn their resistances, immunities, and other useful things.
I've seen both in play to high level.
Close, they actually gave Summon Fiend to a Fighter and he ended up not using it at all because he was 18th level and wanted to make 7 attacks instead, and TBH that was probably more powerful.
Summon Fiend is a 6th level spell and Arcane Abeyance only works for spells up to 4th level. You mean maybe Summon Greater Demon?
And 7 Attacks means Polearm Master with Action Surge because basic Great Weapon Fighting would be 6 with Action Surge, unless there's a crit, and Dual Wielding with Nick would be 8 with Action Surge. If so, that was a bad choice unless the encounter ended in two rounds, which would mean it was easy, because the alternative would have been 4 attacks and casting the spell and even at that level, a Barlgura adds 85 hp to the body count and 4 attacks per round, close to what the Fighter would add if they action-surged every round and at level 18, they can only do that twice.
Sorry, but already the math just doesn't add up in your favor. I could do a detailed list of which choice would lead to higher damage against enemies of various ACs with calculated hit chances and respective averages, but we're both experienced enough to ballpark that already without, right?
A familiar with around 2hps concentrating on Summon Dragon? I've never seen that, but it would be a waste of a spell slot in most of the games I play as a familiar rarely lasts a difficult fight when there is no reason to target it.
Why? There is no range requirement to maintain a summon. The familiar can cast the spell and then fly away, hide behind total cover, or otherwise make itself untouchable. Most dangerous abilities have a maximum range of about 120 feet and you can keep the familiar out of that reach, especially if they can fly and the enemy can not. They just need to remain in shouting range and if a clear, loud voice can be heard from 600 feet, 150 feet distance also works for a familiar. The biggest issue here is that it requires a verbal command, so if your DM is strict and requires the familiar to issue the commands, this doesn't work for summoning spells.
Against an easy foe that you don't need the Dragon for anyway? Sure it would be effective.
I don't do easy combat. No encounter is ever under deadly. As my players say, "If we can't lose, there's no point in having the encounter. You might as well narrate it and get it over with." They're a waste of time to us.
Using 3 5th level slots and a 6th level slot to have party members burn through an enemies LR and then stick one of them is not that powerful, especially since you have to know you will be using them for this particular spell ahead of time.
Of course not, but that's also not the actual situation. You'd use these kinds of spell slots in deadly encounters because otherwise, you're not going to make it out alive.
Instead of all that I could incapacitate an enemy with Selune's Viper on a single successful attack roll with no save, I could do it against every enemy I face for up to an entire hour with no concentration on a single 3rd level spell slot!
But only one at a time since it requires the Magic Action to use it. And it works only against targets that aren't immune to the poisoned condition which is very common. Against all others, yeah, it's good.
Give me my Goblin Enchantment Wizard, with a Bonus Action Hide and Selune's Viper against your party of bead throwers and a Wizard and I bet I incapacitate the big bad first ....
That Bonus Action Hide helps little when the enemy has Blindsight, True Sight, and/or a high Passive Perception. They see you anyway, especially if you want to be within 50 feet and Initiative Bonuses start to creep up after CR 10 very fast, so they most likely hit you before you hit them. I mean, a Rogue with Reliable Talent and Expertise could probably get away with it, but otherwise, you're probably seen.
by that I mean I think I get a hit, probably with advantage, faster than you get 4 failed saves most of the time even with you burning many more slots, more at will abilities and the actions for 4 different PCs.
It can be useful, don't get me wrong, I am not saying it is weak but it is not as powerful in play as you are making out considering all the options available.
At level 10, with a party of 4, your major combat will most likely be against a CR 15 creature, so a Vampire Umbral Lord with Legendary Resistance, Legendary Actions, an Initiative of +14, spells like Command and Hunger of Hadar, and a Bonus Action Sanguine Drain, an Adult Green Dragon with a 60 feet cone weapon and 60 feet Blindsight and a Passive Perception of 22, meaning they see you unless you're behind full cover, a Mummy Lord with 60 feet True Sight, Legendary Actions and Resistances, and Dreadful Glare, or a Purple Worm who burrows under after their turn and probably grapples and swallows the weakest party member - the Wizard - on their first turn. Two of them are immune to the poisoned condition, two are immune to the charmed condition, and one is immune to the paralyzed condition.
Against those, you could have had two Elementals, Constructs, or Aberrations that can exploit the Mummy Lord's Vulnerability to Fire in case of the Fire Elemental, could break concentration on Hunger of Hadar, try to grapple the Purple Worm when it comes up (any creature can grapple under the 5.24e rules), or chase the dragon with their fly speed in case of Beholderkin and Air Elemental. And because of careful scouting with your Divination spells, you'd know what to expect.
With your approach, as a DM, I'd be nervous about a TPK and those are barely deadly encounters for that party of 4 level 10 characters. For an optimized party, I'd probably add some lair actions to not make it too easy for them because an Chronurgy Wizard, a Devotion Paladin, a Light Cleric, and an Elemental Monk make BarBQ out of any of them in less than 4 rounds otherwise. I've had deadly encounters like this where we shut down the enemy so well, we didn't even lose a single HP. Like that one time, we were three level 6 characters against a Cloud Giant: an Elemental Monk, a Divination Wizard, and a Draconic Sorcerer. Giant didn't even get a turn for the first three rounds and that was before Selune's Viper was a thing. With Selune's Viper, that encounter would be trivial today.
But if you are into this Goblin-Hide-thing, I suggest a Goblin Conjurer, Necromancer, or Illusionist. Grab the Telepathic feat, so you can issue your verbal commands silently, and then hide during combat behind full cover out of range of those AoEeffects, Blindsight, and Truesight and issue your commands without ever being seen. Another neat approach is any Warlock with Gaze of Two Minds and Pact of the Chain. Grab an Imp, let him go invisible, and then use Gaze of Two Minds and keep it up. All you need to do is stay within 60 feet of the Imp and you can cast spells as if your were in their space. And because you are casting the spell as if you were in his space and not the Imp, he never turns visible in the process because that only happens if the Imp makes an attack roll, deals damage, or casts a spell which they don't. And since maintaining Gaze of Two Minds only requires a bonus action, you can cast any spell and Eldritch Blast (with Advantage).
But I think we have had this exchange long enough and there's really not much to add. You clearly stated your opinion and I mine and I don't think we're getting any further. I leave the last say to you.