I agree, I either think the range on spit needs to be reduced, or the damage. Or we need more counters.
Sedna's Heal is actually overpowered against UB if anything, removing Spit and healing a huge amount of damage. This can be cast on other players.
Oak's Shield removes it, heals him, and makes him immune to damage for X seconds. This can be cast on other players.
Queen's Bramble Shield has the same cooldown, costs less mana, and will prevent all the damage from a spit. This can be cast on other players.
Erebus's Mist removes Spit and makes him immune to all attacks in the game. He can then teleport out of range just by waiting till his cooldown is up.
There is a favor item which removes all negative effects.
Those are just the actual pure counters.
You also have other options, like:
Unclean Beast is has spit too, for mirror matches.
Regulus can use a combination of mines and snipe to keep a safe distance.
Torchbearer can harrass from a distance, and has a combination of stuns and interupts to help mitigate UB's damage.
Rook is better than UB in melee if specced for it, and can construct a nearly impenetrable tower wall.
Spit is not tough at all if you know how to play.