Last week we tried the primordius achievement on 25man. We oneshotted it. Even though the encounter is quite easy for us we found doing it the achievement way is actually even easier so we'll probably end up doing that tactic every week from now on until we start doing heroic progression
even for heroic, this seems like the optimal strat. I mean, zerg boss, be spread, dot big adds, collect loot.
Except that you see Apex almost wiping to the enrage (only the mage is alive). When my guild did it the same way it was cleaner (8 sec before enrage) but the dps check if you do it this way is absolutely insane and only viable for 25 man guilds who is in the top 30 (currently anyways). The dps check and healing check is much higher than Dark Animus heroic but yes it is stupid easy to execute the tactic provided you have the dps.
The tooltip on the boss is wrong, your damage isn't reduced by 75%, it's reduced TO 75%. That means you lose 25% of your DPS. Eg. you do 100k patchwerky style fight, now you will do 75k.
This dps loss + lack of mutation buffs can make the dps check bit harsh but completely doable by heroic guilds. This is just meta achievement, nobody is going to go for that on progression. By the time you're attempting achievement, you are propably decked out in gear and have tactics in your memory so boss dies on first pull 3 min before enrage. Achievements are for people like this, to make farm content interesting too.