I always found them valuable additions to my Norse teams, but it does depend a bit on your build. Unlike Minotaurs, you can't reliably build them to be roadblocks; no M access means no Tentacles, no possibility of combining that with Diving Tackle, Frenzy means no Grab and less positioning control, etc. If you take a Yhetee on your team, you are taking it to keep your bashing strategy viable against other, more heavily armored bash teams; Claw and Frenzy out of the box are scary for teams that want to get up close and personal with your guys, and adding Mighty Blow with your first level gives you a strong player remover not available on the rest of the roster. In my experience, Norse love to hit but hate to get hit, so they also love intimidation factor to keep from getting sucked into sustained scrums; fouling is one arrow in that quiver, and the Yhetee is another.
The risk is that using him as a beatstick means he'll be using most of your blitzes (particularly to take advantage of Juggernaut if you don't roll doubles for Block early on) which in turn means that when Wild Animal triggers, it hurts twice as badly compared to a safer Roadblock-type Big Guy. Fortunately Wild Animal is the best negatrait for blitzing Big Guys since you reduce it to Bonehead-level odds by attacking every turn but you keep your tackle zone even if you fail. Remember that just declaring a Blitz with him reduces that negatrait, you don't actually have to throw a block or even be in range if the situation just requires him to stand somewhere.
Personally, I'd take them for any "balanced" list that expects to go against heavily armored bash on a regular basis (Dwarves, Chaos, Nurgle, etc.) They would come at the expense of probably an Ulfwerner on my teams- I prefer playing both Runners and Berserkers and letting stat increases influence my playstyle. If I were playing in a league environment against mostly AV7 teams I might trade the other way since Claw is less valuable and Ulfwerners have better skill access.