Arms vs boss below 20%

[Elo]

First off this is my first time posting on any forums like this so I do apologies if i have the wrong idea asking about this here.

I was just simply wondering if even with the high gear levels (264/277) is the best thing to do below 20% to keep rend up and just use overpower and execute?
I have been doing that for a while and it seems to have worked but as myself and other dps start to obtain 277 gear I have noticed i'm dropping below people on damage which I always had little trouble topping.

[Muffin Man]

Actually, keep with rend, OP, MS. At your gear level both of those are out-scaling Execute by quite a bit.

Use execute to replace slam instead.

[Musclebound]

I'm pretty sure when a target drops below 20% the priority becomes rend > MS > OP > Execute. Not sure if bladestorm factors in still or not.