The Yeti is a mean one, even in BfN. He does lack health, but when playing Ops in GW or GW2 and you get a super Yeti wave, it can be a rough time, especially solo Ops in GW2 as the bots get crushed by him quite often. I've used more self-revives and team retries with solo super yeti and bean waves in GW2 than even craaazzy boss hunts!
The elite version in BfN is rough, especially if you lack teammates that know what to do. It's even harder than the elite spooky squash wave can be. Those elite imps as part of the waves are a part of this too.
He's so evasive too. Part of why the Yeti King boss hunt was so difficult is even when you had the damage buff from the imp, you could use a large chunk of it, just getting to the Yeti king!
Not too hard to deal with singly, and yeah, he's not great in the backyard once plant bosses show up, but he will slap you down hard some times.
He is better on snowy maps, part of why I like GW2 the most is there are more variable settings, even if GW felt closer to the original tower defense game in theming.