OK. I did the math for my level 92 zon. Either of these should be multi zons so I included nothing for skill ed%. Both will hit 8 frame multi at about 50% ias. My wf is socketed with 15% ias/ 30% ed jewel. MIN = 38 AND MAX = 545 ON WEAPON.
ZON HAS 500 DEX, FORTITUDE, LAYING OF HANDS.
WF ASSUMING 144% PARTY DAMAGE FROM FAITH ON MERC
(REGULAR / DEMONS)
MIN = 396 / 529
MAX = 5,689 / 7,597
AVG = 3,042 / 4,063
FAITH MIN = 60 AND MAX = 309 ON WEAPON.
SAME GEAR AND ASSUMING LEVEL 18 MIGHT = 210% ED AND LEVEL 15 FANATICISM = 288% ED. SAME GEAR AND 500 DEX.
(REGULAR / DEMONS)
MIN = 838 / 1048
MAX = 4,319 / 5,401
AVG = 2,578 / 3,224
NOW ADD PRIDE LEVEL 18 (AVERAGE) = 315% ED
(REGULAR / DEMONS)
MIN = 1,027 / 1,237
MAX = 5,293 / 6,374
AVG = 3,160 / 3,805
As you can see, without pride, the damage numbers are not even close and WF with faith merc wins. Adding pride to a might merc and faith setup wins by a hair but still does not top the WF setup when it comes to demons. When your merc gets lost with the WF set up, you lose some ed% but a lot of your attack speed which is annoying. With the faith setup, when you lose your merc you maintaine your fire speed but damage drops considerably. Far less annoying this way.
War travlers and max damage charms will increase damage more in the case of the faith set up compared to the WF as they will be hit by more modifiers.
If war travlers would add 100 to min for the WF setup, then they would add about 135 to the faith setup without pride and about 166 with pride. These items could help to close the gap.
As I said earlier, WF with faith act 1 merc is a great chaos runner as merc rarely gets lost and never dies to IM. Other than that, I prefer not to lose my speed once merc gets lost so I like to carry faith and use a might merc with reapers as I do not have a pride. If you are partying with hammer pally's, then I would always prefer the WF as once the high level concentration hits your Char screen, your damage numbers can get obsene.