You're correct that it would be a lot of work, but the dps increase would not be small. If it were, players wouldn't be destroying the Simcraft numbers on Normal Feng.
http://worldoflogs.com/rankings/play...ction_Warlock/
There's nothing on Normal Feng that would cause your dps to be higher than a Patchwerk fight, yet Warlocks who are nowhere near BiS are doing as much dps (or even 4k
more) as the Patchwerk BiS profile. Explain that in any way other than the APL not being anywhere near as good as it could be.
http://simulationcraft.org/510/Raid_T14H.html
The armory for that top parse:
http://eu.battle.net/wow/en/characte...hexse/advanced
Not full BiS, and has received two more pieces of gear since 12/23 when the parse was. Would have done way more in full BiS.
Even using this example, its a 4k dps difference. If you think 4k is a small gain, you know nothing of high level raiding.