Alright, so here's some progression since last time I did one of these.
I got Leoric, Arthas and Butcher to level 10 (in that order).
Leoric is just pure fun.
This is how you design tanks *
looks at Muradin*. When I started playing with him, I thought that he was absolute trash. But upon understanding how insane his Drain Life ability is, it pretty much clicked. On top of that, his bail out (E) is in my opinion the strongest gtfo in the game. Both his ultimates are decent, although I did prefer the 3-Swings. Not counting Tyrael (who also surprised me btw), Leoric is my favorite warrior in the game.
I honestly felt that Arthas was a solid mid-tier tank with the ability to unexpectedly burst your opponent down. Both his ultimates are pretty weak though. Sindragosa feels underwhelming despite getting value out of it (Haunted Mines, 4 towers hit) and the Raise the Ghouls barely works in the extremely bursty meta that we have today. Definitely solid as a character though.
Butcher plays exactly how I expected him to play. This was one of my most anticipated hero release and I got pretty much what I wanted out of him: insane burst with pretty much no way of getting the hell out once dedicating yourself to an attack. The most satisfying thing with Butcher was oddly enough being able to sneakily solo the bosses at level 16. Other than that, I can pretty much confirm that there is nothing worse than dying as Butcher before level 7, only because you lose all dat meat.
Fun-tier-list
God fun: Zagara, Kael'thas, Sylvanas, Jaina
High fun: Thrall, Zeratul, Valla, Kerrigan, Falstad, Tyrael,
Leoric
Medium fun:
Butcher, Johanna, Tychus, Anub'arak, Malfurion,
Arthas, Illidan
Low fun: Li Li, Raynor, Nova
Trash: Muradin