Maim and storm's eye is available with or without defiance so neither are making up for the damage penalty. There's the damage a WAR does without defiance while using maim and storm's eye and then they do about 25% less damage with defiance on. The damage penalty is still there in full effect.
War vs. PLD can be deceptive when considering damage in their DPS stance. War's do a lot more big hits, but their only off GCD ability is brutal swing (not always able to be used). PLD makes up that damage with more hits, coming from extra auto-attack damage via sword oath and powerful off GCD abilities like spirits within and circle of scorn. In addition, fight or flight is not quite as powerful as berserk, but it lasts for 50% longer and doesn't cause pacification either (causing you to miss 1-2 full GCD attacks).
You also shouldn't really count the WAR's max dmg combo (SE->BB) unless you're talking about a burn phase where you don't care about damage received. WAR OT should be doing SE->SP most of the time to keep 100% up time on both debuffs.
Kitru did the math, it comes out slightly in the PLDs favor with Sword Oath vs WAR without Defiance when both classes have access to storm's eye, but it's still very close (within a few % of eachother).
As far as who loses out more, it's definitely the PLD when swapping to tank. The PLD loses the extra sword oath damage, then loses another 20% damage via shield oath, and since they're getting hit all the time, spirits within will either not be doing its full damage, or it needs to be delayed a few seconds to use when at near full life. The only thing the PLD gains back is shield swipe after blocking, which is a small DPS buff (but not huge). War on the other hand only loses that 25% from defiance. However, they have a number of abilities to mitigate this. Wrath stacks grant more crit, unchained can mitigate the defiance buff for a set period of time, and inner beast is a very high potency attack not subject to the defiance penalty.
Thus, since WAR has the highest potential damage while tanking (they lose less when going to defiance) and PLD has slightly better damage while not tanking, the combo with the highest DPS potential is WAR MT + PLD OT.
HOWEVER ...
The other problem with WAR MT is that it's very difficult to keep the SE debuff up 100% while tanking with a PLD off tank unless you drop the SP debuff. To keep both and have 100% up time, you need to be able to tank using the low threat SP->SE combo. This only works if the PLD has spent a good portion of the fight off tanking something else, giving the WAR a significant threat lead, allowing him to use the low threat combo. If this is not the case, you'll probably need to work the BB combo in at least 1/3 of the time, which means that the SE debuff will now only be up about 60% of the time. This results in around a 3-4% loss in DPS for BOTH the WAR MT and PLD OT. In this case, the numbers may be more equal, but it would require a more involved analysis that I'm not willing to do.