I have a hero and she is a glass cannon. She hits hard at range but can only hold off more than 1 mob for a short time. Her melee damage is 1/3 her ranged damage so once 1 mob gets on her her dps drops hugely. She can die to a swarm of small mobs before she beats through them if out of range of towers. Some mobs can also solo her 1v1.
She is roughly equivalent to a Slime Trooper. The trooper has more hit points and no ranged attack but hits in melee for the same amount the hero does at range.
I think we need more other types of heroes so there isn't just the 1 and so different heroes are better on different maps.