Overwhelming Power: stack or not

[Severlia]

Hellow fellow Mages,
I came here with maybe simple question, but it bothers me quite a bit. The question is, should I stack overwhelming power trait?
https://www.wowhead.com/spell=266180/overwhelming-power
With corruptions listed below:
24% haste
12% mastery
4% critdmg
R3 haste proc
Sims say to stack it, but sometimes it falls behind on specific fights