could be worth to switch to berserker stance when the aoe dmg is very high. when they switch pheromones go back to battle stance since there is not very high dmg when the stack of pheromone ain't high.
As others have stated, it's ideally in battle stance until crushes, in which you switch to berserker stance (the stun will pretty much keep you in place till cd on stances is over). Numerically, my average rage gen is 8.8 per second (ideally), so you'd assume 4-5 in berserker with no incoming damage. which means you'd need to be taking 3-5% of your health per second. Since pheromones hits every 2 seconds, it'll take each tick to do 6-10% or more of your health per hit. Meaning, it'll take around 40k damage every two seconds to be worth it. This is pretty easy to get (but this is also if you are at exactly at 400k hp with buffs). This is also subject to variation due to white hit crits, enrages, shouts, bts, etc, so take itwith a grain of salt.