I've got a grift ~30 pet doctor. Pets getting one-shot at higher rifts becomes an issue, and then it gets crazy for gear, as SMK + Tiki becomes the build of choice. I think that transition doesn't occur until mid 30's or so.
Haven't focused too much on crusader or wizard to have definitive opinions. My crusader got into T4 pretty quick, though. But that was barb hand-me-downs and other things that wouldn't be applicable to seasons.
My wiz is still ~T1, could probably run higher, but they're so squishy due to lack of killing power, and that's with 700K paper damage. If I cared some more, I could probably get my wiz into T6 without too much work. I only need one more piece of firebird's. I already have a maximus, although it kind of sucks.
My monk just jumped right into T6, and that's a lot of luck, I guess. Got an incense torch and decent cindercoat that just let me melt stuff.
I'm going to run monk again for the gungdo. Of the season exclusive legendaries, it interests me the most. I could be tempted to do a DH for that bow, but then the chakram quiver becomes required, I would think.
I like the idea behind the crusader belt, but I don't want to level another (it would be my fourth) crusader.
I wrote a lot. I'm a little bored.