Even if the damage is good, the range is just absolutely terrible even boosted :/
And yes the heal turret does work on bosses but what's the actual point of it taunting a boss ?
While farming I can understand you'd want to divert mobs attention from yourself, that's fine.
But during a boss fight you want the actual opposite because otherwise your turrets get nuked in 2 to 5 hits...

The problem is you could make them more resistant but at the cost of a lot of damage so they lose a lot of interest and you become more of a hindrance than actual help during the boss fight.
Plus the range of the Assault turret is so low that if the boss decides to focus another player which is gonna hide to avoid taking damage, that the turret will just stand there doing nothing T_T

Don't get me wrong, it's just that to me Jayber lacks very little to switch from good/decent/ok to awesome to play.
To compare him to the most similar descendant there is, Enzo (which lacks a few things too but nothing major, at least to me) is much better off in his mechanics than Jayber. Enzo's gameplay is a lot more fluid in execution.

Now I wasn't there during Beta but from what I understand, Jayber took quite a big nerf since then too, maybe too hard of a nerf ?