Can a character that has multiclassed as a War Domain Cleric and Blade Pact Warlock attack 3 times in a round?

Question

In DnD 5e a 1st level a War Domain cleric gets "bolts of inspiration" that allow an extra attack as a bonus action. This ability can only be used a limited number of times per long rest.

At 5th level a Blade Pact warlock can get the Thirsting Blade Eldritch invocation which allows the warlock to attack twice with their pact weapon.

If a character had all the prerequisites could they attack 3 times in one round? Twice with the attack action and once as a bonus action.

I know that extra attacks from multiclass do not stack. Is this an exception to the rule? Given the limited nature of the War Priest ability I don't think it would be terribly unbalanced but a character could occasionally elevate their burst damage.

Answer 1

Yes, you can make three attacks per turn, but it's not that special

There aren't really any rules to clash here. The War Priest feature requires you to take the Attack action (and a usage of the feature) to use a bonus action option, and independently Thirsting Blade (or any Extra Attack feature) modifies the original Attack action. The multiclassing rule re Extra Attack concerns features which modify the (same) Attack action, that's not what War Priest is doing. The net result is a limited number of turns per long rest where you get a third weapon attack as a 6th level character.

But getting that isn't particularly exceptional at 6th level, as there are a number of ways to get a bonus action attack (on top of an Attack action with two attacks) with different riders: Two weapon fighting, being a Frenzied Berserker Barbarian, arguably spiritual weapon, being a monk, Crossbow Expert, etc.

As for this being powerful, the power is really just in the War Priest feature. It gives an additional resource (it's own uses) of quite powerful attacks (if using a two handed weapon). Just the 1st level War Cleric is a clearer demonstration of this, having two full attacks (for that same number of turns per long rest) at first level. It just happens to stack with Extra Attack features, including Thirsting Blade.

Answer 2

Thirsting Blade says (emphasis mine):

You can attack with your pact weapon twice, instead of once, whenever you take the Attack action on your turn.

The War Domain’s War Priest feature says (emphasis mine):

When you use the Attack action, you can make one weapon attack as a bonus action.

So yes, a limited number of times per long rest, this character could attack three times if they are using their pact weapon, using an action and a bonus action. These don't conflict at all, one feeds right into the other. I did a google for something official, didn't find anything, but found a number of hits discussing this exact build tactic.