The troop is going to be filler regardless because of how it is designed, but the numbers seem like they were balanced for early 2015 Gems of War, not late 2017. Not everything needs to push up the power curve more and more, but this one only barely edges out Berserker on some fronts and loses on others, and Berserker is already pretty far down the power scale.
One of the larger issues with this troop is not just the low damage per mana ratio, but the fact that most of the time you’ll lose the turn casting it. In order to set up for a guaranteed extra turn, you have to “waste” half your potential damage. Always losing the turn for extremely low damage pokes is not really a valid strategy even in early game or arena unless you are already running away with a good board. If Claw Dancer, for example, always got the extra turn but gained 4 attack when she killed, she would still barely edge out the common “Goblin” early game, as a Ultra-Rare.
But, as I said in the spoiler thread, she looks like a decent fodder blocker covered by a summoner. She has agile, high base attack, and won’t heavily mana block if you want to just put her up front and ignore her spell completely. Then again, this something you could also use Peasant or pre-buff Dwarven Miner for other benefits (jinx on peasant, stone link on dwarf), but using a “real” troop generally ends up being better in pretty much any situation and both red and brown already had viable fodder blockers (fire bomb, lamia, keghammer). Outside of Guild Wars, you would generally be more inclined to just pick an impervious or stoneskin (or a high power legendary like Khorvash where possible) that doesn’t block your general mana flow at all.