I don't use Whirlwind much either, but I still consider it useful, the moves that are being removed I still consider useless
Carnage Marauder's have a harder time with rage than you realise. Force Choke is used sparingly at higher levels if at all... mostly not, retaliation is used sparingly too, if at all. For us things are focused around Gore and Massacre and firing off Force Scream when it can auto-crit. Smash is only really good for trash mobs, however only really effective when everyone else is aoeing them down too. Generally, people who play a Carnage Marauder all agree that you have to be extremely careful with them otherwise you'll become rage-starved very quickly... even more quickly in 2.0.
Requirements aren't the issue, there are a lot of times when you have to use one ability to build onto the next, wait for things to proc, etc, with every class. Some classes need more management than others in this area.
Tell you what though, I'll put Tumult back on my quickbar for my assassin and play around with it before 2.0 hits... there's plenty of time before that happens.