I’ve been thinking about this lately as well and was about to post about when I found your OP. I’m glad to see that someone else has suggested it. I’ve brought up before (though I’m sure I was not the first) the need to make AOE attackers more relevant for titans, and I think something like this makes the most sense.
There are several ways they could give players attacking certain titans multiple targets to hit. Several titans already implemented in the game have multiple heads–namely the Gorgon Queen and the Raging Hydra. They could easily be tweaked to have more than one target (say, 4-5), allowing AOE attackers to have the full potential of their attacks released occasionally against titans. The Kraken could also be made to have multiple points of impact along his various tentacles.
There’s a not-so-short list of other multi-headed beasts and monsters from legend and myth that could be added as well. Even just looking at Greek mythology: They could create a Cerebus, the multi-headed dog that guards Hades. Or a Chimera. Or the Scylla. Or the Ladon, a dragon sometimes portrayed with as many as 100 heads, could be a great titan to take AOE hitters against.
As another option, they could also include minions for certain titans, like the Goblin King. Perhaps he could be surrounded by 3-4 (or more) much smaller goblins which, if killed, would be replaced, say, three turns later with a fresh hoard of guards. AOE hitters could help keep a team alive by wiping out oncoming hoards so that single-hitters can be kept alive to dole out damage to the King.
I really think it’d be a fun option. It’d give folks a reason to occasionally bring in those slow-charging, AOE hitters and would offer something new to alliances when fighting titans. It also wouldn’t seem to require much on the developers side, as many of the basic mechanics are already implemented elsewhere in the game.