That's true, but juggs with wrestle gives you the option of not going down when you get both down result.
Besides if you look at it from another angle also MB is wasted to some extent with wrestle in that if you get both down you don't get to use the skill.
Anyway thanks all for the input.
If all of you prefer MB there must be some reason, I'll think about it.
Mighty blow increases your odds to cause more damage quite a bit. Combine it with frenzy and you have over 80% odds to knock something down with neat odds to cause some pain, assuming you have two dice on both hits. Since witch elf is ag4 they can sometimes opt to dodge out with a 2+ after blitzing, that's reasonable enough gambit to do occasionally. Also look for chain push opportunities, especially with 2 guard you could clear quite a bit of path while still not letting your opponent to block you.
You won't be blitzing with it every turn as position won't allow it in most cases. But for the turns you can do it it's so great value to attempt a knockdown twice. In theory if you could blitz with non-frenzy mb every turn, the witch elf has sort of done her job by doing it just 8 times in a game (not even counting all the other position worries for your opponent regarding frenzy)
Your opponent needs loads, loads of guard and high STR and precise positioning to not make it feasible to blitz/block with the witch elf at all. That scenario is relatively rare and if it happens, you're screwed no matter what most likely and need to roll loads of d6 with the team anyway to make stuff happen.
In most situations it's very unpleasant to play vs witch elf and it is a high priority foul target in many games. You can't leave players alone against it because the witch will target them recklessly.
Too tight formation preventing feasible frenzy blitzes and one of the flanks can be abused more often than not.
