Nah, that's perfectly fine. Well not perfectly, but agreeable because the developers want cash, and the game wouldn't exist without it.
What hurts the game is the quantity of new heroes, and thus severe problems with heroes mechanics/balancing/bugs. Take Spider for example. The hero's completely broken by design. It's absolutely useless against non-tasty group, and that's unacceptable. It's super OP against tasty group with full energy, and that's unacceptable. And now, without runes she would be fine. With starting energy runes she's absurdly overpowered, due to freeze frame bug, and thus was must have to be competitive in fight pit/coliseum. But with bone's changes spider has become completely obsolete in pit...
And basically the same can be told about several heroes. Plant Soul's mechanic is flawed, and it's buggy as hell, I've had a dozen of fights where everybody was stuck until the end of the fight because of her. Master Thief's mechanic is flawed, her purple gives too much ridiculously powered RNG. Not to mention it's buggy as hell too, I've seen a lot of fights where she would absorb crazy damage from enemies, but not shooting back, and just dying in a few seconds doing nothing.
See the problem is not in heroes themselves. When you have the task to invent 3-4 heroes a month without objections, you just don't have time to think of proper mechanics and test them thoroughly. Things just quickly go downhill with all that flawed and buggy stuff.