If you plan your gear appropriately, you won't go over hit/exp. If you just take every item that drops, you may run into issues. Either way, Haste doesn't look to really be increased when using the rppm trinkets. Simcraft values don't really change, and from various spreadsheets with rppm trinket formulas in them, it takes a lot of haste to dramatically increase the avg proc stat.
Feather and VP trinket are causing Unholy FB to skyrocket right now, aside from just being good. Using Outbreak at the tail end of both, with potion, is in the neighborhood of 20-24k+ Str filled diseases. It's pretty gross, and if you can manage it right, some serious DPS. I'm wondering if/when Festering Strike will stop extended the snapshotted AP of diseases.