I think if Agonizing Blast applied to each die of damage, the damage cantrips that have useful side effects would be as good as Eldritch Blast. Fire Bolt would remain over-shadowed due to the damage type (about 80 core foes resist or are immune to fire, versus 1 that is immune to force, not to mention that spells like Absorb Elements have no effect on force).Considering that eldritch blast is the best cantrip in the game without any invocation support (as you said, high range, force damage, and the ability to multi-attack), I don't see how giving the other cantrips the same benefits via invocation could possibly be considered OP.
If you really want to help out other cantrips without removing Eldritch Blast, maybe make it so that Agonizing Blast gives +Cha to damage per die of cantrip damage. EB is still slightly better, but the other cantrips will give a better chance of big hits (at the cost of whiffing more often).
My motive for reviewing the spell at all comes from vocal player concerns. We have two Warlock players. One of them has played their character from level 1 right through to level 11. The other joined at level 4 and played through to level 12 from there. I think their experiences are worth listening to.The only real questions here is
Is your desire to change the spell also desired by the warlock player?
Agreed. Where I find myself moving toward is making an adjustment not to the Blast, but to the Invocations. House ruling they apply to only one damage die, but that they also apply to all damage dealing cantrips.Then the problem is *not* the thing you are kicking out of the game but the feature that is modifying it.
The rapier is not needing to be banned because of the sneak attack damage it gets, right?
So, thats my point.
Instead of banning Eldritch blast change the feature so that its working with Eldritch blast in a way you find acceptable.
Change the feature to "once per turn" not "once per die" if the "per attack" one bolt vs three bolts issue is a problem for your warlock happiness quotient.
Expanding the Agonizing et al to cover other types of cantrips is to me not a problem - after all - the blade pact benefits apply to more than one weapon type right?
Maybe have a second invocation that allows you to apply the various EB boosts to other cantrips - like how you can take Improved pact weapon and gain ranged weapons to conjure up - etc
but banning eldritch blast from everybody else because the warlock makes it not work how you like seems like blaming the rapier for the sneak damage preventing all those greataxe rogue concepts from being used.
Yea, I think there's a key question there that has to be answered before you can really houserule EB in any direction: Is the multi-attack component of Eldritch Blast a feature or a bug?The thing is, it feels like Eldritch Blast at the table is a bit better than it needs to be to remain viable. The combination of a target per damage die, force damage type, range, and per bolt bonuses, turns out to be really strong. Over time, the average damage from say Fire Bolt compared with Eldritch Blast sans Agonizing Blast is the same, albeit Fire Bolt is spikier (its damage comes in bigger lumps) and is more often resisted. However, the efficiency of being able to switch targets, and of course Agonizing Blast, make Eldritch Blast much killier.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.