We can't really speak to your other raid members, but there should be a significant jump in DPS at execute phase - sim yourself and check out the dps over time graph. Also find your shift key.
during execute phase(25% and under), i have been doing as the guide suggested "Once the boss reaches 25% HP, begin to channel Drain Soul while continuing to cast Haunt on CD and refresh Bane of Doom when required. Drain Soul will automatically refresh Unstable Affliction and Corruption when it ticks, so you should not need to worry about this."
I have been looking at my logs carefully, But i don't see a obvious DPS increase from that. my dps usually at the top before execute phase, when the boss die, i always fall behind the arms warrior and fire mage in my raid group
Is there a trick i am missing or getting ahead by warrior and fire mage during execute phase is normal?