RPPM still scales with haste, it's only double dip mechanics which got changed. The likes of your legendary meta and cloak are based around haste scaling.
I've always been a little hesitant to blindly go with Shadowcraft's ep values as haste seemed inflated. Even with last patch's RPPM mechanics, I always felt that in a live-raid scenario, realistic mastery was still outperforming realistic haste. Also, if anyone follows the world-class rogues from the various top guilds, there's actually a really decent mixture of those stacking haste and those still stacking pure mastery. If those guys aren't purely going one way or the other, that leaves me more inclined to think that it's a personal, play-style decision and not an absolute necessity.