Depends on class and playstyle. If you're referring to druids, it's mainly if they play boomkin because of the faster globals and dots, which in a mid fight can amount to more dmg than vers stacking. With that said though, it's a trade-off. You obv. won't have as huge oneshots and tankiness, but if you have others to substitute that for you, or if you run double boomkin for insane pressure, then it makes a lot of sense to go haste.