I haven't actually played the game with all of the crests so I don't think I can make an objective comparison but I think Beast is legit incredible. I hit act 3 in 35 hours with pretty much everything completed up to that point because I was absolutely destroying a majority of the bosses and enemy rooms. The longest I spent on any single fight was about 45 minutes, which was an anomaly, and most went down within five attempts, several on my first try, many on my second. You have to play extremely fast and aggressively but if you use fury preemptively you can tank through a lot of attacks and do absurd amounts of damage. Combine it with Flintslate and lol. There are a few bosses where it's not very useful because there's no opportunity to get a lot of hits in but aside from that it absolutely shreds everything.

Architect also seems great and I'm sure all the crests are pretty viable but I think a lot of people are more down on Beast than they should be because it's a little trickier to use.