Genuine question here. Why aren't some bosses designed as multisegmented or with multiple hitboxes?
tl;dr: Class variety would be improved in applicable boss fights if some bosses were given multiple weak points that could be hit with a single ability, given optional weakpoints that only certain classes can fully benefit from, or occasionally spawn weakpoints temporarily that certain classes could take advantage of.
Before you Mage speech bubble me, please hear me out.
I get that some bosses like Harrakfar and Orasomn where you do have to kite should be single segmented for practical reasons. I also get that some bosses should be single segmented based on design.
However, what's stopping a boss that contributes very little with its melee attacks, moves very little, or is literally a giant hitbox from having multiple segments or multiple hitboxes. Throwing out a few here, Sirius, Vesp, or even Ru'Ten to a degree.
I really don't think this is a shocking thing or something unprecedented. In fact, I feel like it's quite a common solution in other games to solve the single target vs aoe issue. It's quite common in Turn Based Games to have Bosses that can be hit multiple times with a single move to prioritize different abilities at different points. Other bosses in action games have multiple parts on their body (arms, body, head, etc.) to give a little more priority to AOE abilities.