I don't really see spit as totally overpowered, although its range is a little gnarly.
More, I see the problem with Ub as a whole is the synthesis of all his abilities. The slowing claws, the spit (primarily because of range), make a UB very, very difficult to flee from. This wouldn't be nearly as big a problem, except theres another aspect of this game that puts this issue into overdrive, and thats hp stacking.
You see, in my view, by the end of the game the 'burst damage' is not lackluster persay, but it becomes less and less important as everyone begins to run around with 5k hp. When everyone has a massive amount of hp, burst becomes less powerful then efficiency, and that is what the UB has in spades.
This is a demigod that can DOT, stun/drain, and snare you. Meanwhile, he's attacking more quickly then most demigods, and moving more quickly then most demigods.
(Shout out to eq1 players - Necromancer, anyone?)
Think of it like a DND 3.0 - 3.5 wizard. You have a certain number of spells, and thats it. When dealing with something with low HP, burst is your bread and butter. If your dealing with a titan with massive hp, you need to use your resources more wisely, and focus on debuffs/dots/EFFICIENCY.
This is what I see playing out when I run up against UB. Its actually something that has occured in many games before.
Tl;dr Its not an imbalance with spit in relation to other abilities, its an imbalance in item/hp stacking/burst damage relations.