So you can't dismiss CE only on the grounds there are better things to do with your bonus attack. CE cruically removes the risks of entering melee. That it provides the equivalent of two-weapon fighting (the attack mode) as well as two-weapon fighting (the fighting style) is, well, not just "a bonus" since it's better than that, but still... What I can say, however, is that just focusing on the use of bonus action is comparing apples and oranges.
CapnZapp, you specifically asked me to explain why I felt CE was a poor use of your bonus action. If you wanted to say, "But I like the other parts of CE more," you could have said so up front. But you asked me to explain my remarks on the bonus action part, which comes down to "mobility, hiding, and meat shields are all better". (There are also some niche cases of pseudo-meat-shields like Flaming Sphere, but I'm not a fan of those in the general case. Maybe in certain campaigns I would be.)
"Taking zero damage in a fight at the cost of a bonus action *snip*" - could you be more specific, please. What exact build choice and what exact combat action are you talking about here?
You snipped the part where I mentioned the other part of the cost: a mobility spell (e.g. Expeditious Retreat) or Skulker + two levels of Rogue.
There's not an "exact build" because there's not only one way to do it. There are some general principles that apply: taking no damage by keeping out of range or being untargetable is better than a modest boost to damage. Some examples of applying these principles include:
A Mobile Sharpshooter Eldritch Knight archer who uses Expeditious Retreat to kill anything with a 40' move or below, and against anything with less than 80' move can switch to a rapier and kill it that way instead. (Thanks to Mobile feat and bonus action Dash for 80', of course--I'm not sure how much I need to spell out so if I skip over something I should explain let me know.)
An Skulker Arcane Trickster 3/Battlemaster X archer who sneaks around in the dark killing things. Darkvision turns darkness to light obscurement, and Skulker lets you hide in light obscurement, so Skulker + Cunning Action + Stealth Expertise lets you hide with high reliability from anything that relies on normal sight or darkvision, which is most things in the MM. So you shoot the thing with advantage (probably with -5/+10 if you happen to have Sharpshooter too) as many times as you have attacks, then Hide and move to a new position. If it wants to attack you back it has to randomly pick a position to attack in the hopes that you'll just happen to be there, and even if it chooses right it's at disadvantage on its attacks because you're hidden from it. (Unless it's Alert, but monsters hardly ever are Alert.) If you have to do a fight in broad daylight you use your Arcane Trickster spell slots to cast Fog Cloud and just hide inside that instead.
An Eldritch Knight 11/Rogue 2/Wizard X could do the same trick using Greater Invisibility instead of Skulker/Fog Cloud. (You'd probably go Fighter 1, then Rogue 2, then Wizard 7, and then spend the next ten levels levelling up Fighter to EK 11.)
As for Expeditious Retreat, yes, it's a bonus action spell. But you can't cast that every round (and you don't want to either). So it is by itself a poor substitute for a bonus attack. Or more to the point, nothing says you need to choose here. If you have this spell, you can cast it round one, but then make bonus attacks other rounds.
Sure, you could take them both. But I generally find that my bonus action is already quite busy, busy enough that spending a whole feat on a modest damage bonus attack feels like a complete waste. I'm probably affected by the fact that I
also think the Crossbow Expert ruling is cheesey. But remember that I'm responding to
your claim that Sharpshooter + Crossbow Expert is a dominant strategy which renders others nonviable and unnecessary. The burden of proof is on you to show that I'm somehow missing out by not going Crossbow Expert.
I'm not missing anything important.
Skulker seems to me like a way to supply advantage, and as such, it's not a bad option. However I have several caveats: a method that grants advantage to everybody is far superior to one that just grants advantage to one hero. So skulker is on par with barbarian reckless attack in that regard, but worse than, say, Hold Person or Ki Stun.
Also: hiding (not the "getting advantage" part, but the "removing yourself as a target" part). I'm afraid hiding has a requirement, or it is fundamentally flawed. That requirement is - everybody needs to do it, or the monsters will simply hit someone else.
That's close but not quite accurate. Everybody
who is engaged with the monsters needs to do it, or the monsters will just hit somebody else. It's true that an all-Mobile party is fantastically fun and easy to play well with; but even if you've only got one guy that's a Mobile Shadow Monk, your party now has a trump card that beats many common situations without resource expenditure. You need good enough reconnaissance to know when to
use that trump card, but recon is another topic for another time.
Suffice to say that three PCs engaged with three Displacer Beasts can still benefit from hiding even if only two of them can hide, to the extent that the third PC can disengage himself from the monsters. It could be that he's a heavily-armored AC 20 Life Cleric who drops a Sanctuary or Shield of Faith on himself and then Dodges; or maybe he's a Sorcerer who Disengages and casts Expeditious Retreat to flee out of their range; or maybe he Levitates; or maybe the geometry is such that he was far enough (30'? 120'? 600'? remember that the PCs control this) behind the point men that he never has to enter melee in the first place.
I'm obviously not making the claim that hiding prevents you from ever taking any damage ever. (Although I
have had to introduce some rule variants to tone hiding down a bit, including letting certain monsters with blindsense like Black Puddings ignore Dexterity (Stealth) hide attempts completely.) I am claiming that under reasonable assumptions, it's a very strong tool to have in your toolbox and better than Crossbow Expert is.
And you don't want to make the monsters focus their fire any more than they already do.
Actually, if you can control who the monsters are going to focus their fire on, it's great! My players
love knowing who the monsters are going to focus their fire on (I use a declare/act simultaneous initiative system, so dumb monsters don't get the chance to change their actions in response to PC action declarations.) Dodging is free.
(If your DM always plays monsters efficiently, this caveat disappears. But I would bet most DMs don't)
I certainly don't. Unless they are paranoid supra-geniuses like Mind Flayers--and BTW, the "efficient" action from many monsters is often "run away and live to fight another day," which is frustrating for players. So not fighting efficiently is an important part of running a fun game.
The basic building block, taking Rogue levels, on the other hand, is probably a truly strong tactic. The way Rogues get to use their bonus actions is certainly very useful, bordering on ridiculously strong if everyone in the party has a means to gain such high mobility.
"undead meat shields" - no objection there. When it comes to spamming conjurations it kind of breaks the game in its own way. I prefer to simply not to think about it, which doesn't mean your suggestion lacks validity. I wouldn't call that a tactic based on your bonus action as much as a tactic based on conjuration spells, though...
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In the end, though, it doesn't matter, since SS/CE isn't primarily about the bonus action, but about 120 ft "reach".
I would more consider your suggestion to take Rogue levels (for the hiding, mobility) as something you might consider adding on top of ranged, rather than replacing it.
If you've already committed to the Rogue levels, CE feels like a waste.