I thought I remember reading somewhere not to long ago that they were doing a slight bit of movement with the Yeti in addition to the strobe effect. As you said, just moving the arm up and down. I could be wrong however and can't remember where I read that.
I do hope that once Avatarland opens up and gives DAK another e-ticket to divert traffic that they will shut down EE and fix the Yeti once and for all. I did get to ride EE numerous times when it first opened (I was a Marketing CM at the time) so got to see plenty of A-mode Yeti. While it has certainly been built up in everyone's mind since they moved to b-mode, it was very cool. The swooping/grabbing and dipping down of the character never failed to startle me as every time it seemed like that giant arm was actually going to hit you.
Maybe when they do eventually fix it they can even upgrade it. Would love some trim brakes in that big room to slow the train down, some more dramatic movement/lighting on the Yeti, etc to build tension.