I've decided this is the hole in my Steadfast/Sickle quiver I'm looking to fill this year. I'm leaning toward an old Mantra. Here's my thinking based on some skis I've tried in wet, cut-up, heavy conditions (mostly A-basin in late April/May):
Steadfast (90mm): pretty good, and what I defaulted to last year. I wished they were a bit stiffer and wider, though. Steadfasts are by no means soft, but I notice the lack of metal in these conditions.
Sickle: (110mm): I tried these a couple times last year and pretty quickly switched back to my Steadfasts. They were just too soft and felt like they folded over when slammed into a slush bump I wanted to plow through. The Sickle is not a super soft wide ski by any means. It does great in cut up winter crud, and at relatively high speeds on groomers. There's just not enough there for these conditions. 110mm is also too wide for bumps, and slush bumps are a huge part of the fun on a day like that.
Kendo (89mm): even better than the Steadfasts because they are stiffer and have a longer turn radius. Kendo would be a great choice. I'm thinking there is only benefit and no penalty going with the Mantra over the Kendo, though. I prefer the Kendo in bumps, I don't think the Mantra's extra width matters as much in slush bumps.
Rossi S3: Too soft, but still pretty fun if you keep your speed down. The extra length allowed by the extreme rocker is kinda a wheelie/endo bar to keep you going over back or forward. A nice benefit of the 186 S3 skiing like a 175. It's a nice width and easy flex for slush bumps too, again as long as you keep your speed down.
(Old) Mantra: I haven't been on it in maybe threes years now, but my memory is that wet, heavy, cut up glop are its ideal conditions. Is my memory serving me correctly?