Berserking Vs. Mongoose - EnhancementFollow

Weapon Enchants

Information on weapon enchants courtesy of Rounced.

Mongoose
Proc for 120 agility and 2% haste. Stacks if both weapons are imbued. Proc mechanic thought to be set to 1 PPM. Works out to approximately 40% uptime (based on WWSs). Does not appear to scale down with level. 2% haste = 65.58 haste rating. So each proc should be worth (65.58 x haste EP) + (120 x agility EP) = 302.4 EP for a value of 121EP after uptime.

Berzerking
Provides 400 attack power in exchange for 25% of your armor when it procs. Does stack if used on both weapons. Proc mechanic is reported to mirror mongoose (and current findings appear to validate that model) so it should have approximately a 40% uptime. 400AP = 400EP. With uptime should be worth 160 EP.

Accuracy
Provides 25 hit and crit rating. If you are under the spell hit cap (taking this enchant into account) then it is worth (3.2 x 25) + (1.7 x 25) = 122.5EP. If you are over the spell hit cap then it is worth (1.6 x 25) + (1.7 x 25) = 82.5EP.

Berzerker is the best option to use on at least one, if not both, of your weapons. However unless you have separate weapons for PvP the debuff is going to be very painful (400AP versus giving every melee the equivalent of 385 Armor Penetration Rating). Mongoose is still a great second choice and if you can use Accuracy to just hit the spell hit cap it's an acceptable option as well.

IIRC, the armor debuff from Berserker was reduced from 25% to 5% in 3.0.8, which would make it the clear winner for all but the most hardcore PVP addicts (maybe even them, just not up on the current state of high lvl arena).