Berserker is weak.
Fury health regen should scale better. Either make it % health regen instead of flat health regen, i.e. regen 15% max HP every 5 seconds, or make it scale exponentially, i.e. regen (points/5)^2 every 5 seconds.
Magic Defense is a dead upgrade.
Change it to something that increases shock duration by 0.04 seconds per point.
Shooting Defense (when we get VH) is a dead upgrade.
Change it. Maybe something that increases the effects of weapon runes by up to 75%.
Ranger is the only character that gets no unique/interesting training options.
Consolidate Shooting Speed and Shooting Power into Shooting, which gives 2/3 the effects of both? Remove Max Mana upgrade, and lower mana cost of shortbow charged attack to compensate? Add Pet Power, which increases pet movement speed, decreases time between teleports & revives, increases damage, increases health? Add Max Health upgrade, to give Sword Ranger some love?