QUOTE(nec1986 @ May 11 2015, 16:24)

Not so much. Good force cost 5-10m and 10 is probably excellent rolls which is very-very hard to find. I saw many with forge around 8m.
So, ive checked prof mitg reduction. Its quite interesting.
First. I checked different classes.
Celestial with 66% holy - 522 average
Mech with 72% holy - 415 average
Humanoid with 51% holy - 843 average
You can see if we completely delete mitg than get 1537, 1483 and 1721. Because we can get different mobs with different defense than i decided to check only exact one. It was Cracker jim.
352 divine, 1063 mdb - 415
429 divine, 1172 mdb - 557
579 divine, 1377 mdb - 993
707 divine, 1548 mdb - 1682
Because i have different mdb its better to scale all to 1k. This way we get 390, 475, 721, 1086. Its huge difference. In first example i dont have any reduction because my prof is lower than my lvl. So full damage is 390/(1-0,72) = 1392. With 429 divine i should get 4,42% mitg reduction, so check again and get 1466. 1380, 1427 for last 2. Looks quite close so we have quite simple residual in mitg. Already we can see if mob has huge mitg than we cant reduce full amount with only our prof. This mob has 72% and i can reduce only 50%. 22% is still very solid, because its only 7800 damage out of 10000. Also if we use imperil on high diff we still should have very high prof.
I got some numbers from mozilla browser`s post. He says average mitg for mobs above 1000pl is: 50,47,46,45,42,40 for fire/cold/wind/elec/holy/dark.
But that mostly means someone has very low and all others high. For example for holy quite ordinary is 50-60. Sometimes 40 or 60-70 range and sometimes like 7-20 and that low reduce average. But generally 2 prof reduce near whole mitg and only some relatively rare mobs have higher.
counter-resist effect of magic proficiency is linear, so we don't need to feel like we have to reach the proficiency cap or stick with all phase.
Specific mitigation reduction of magic proficiency is exponential, so that is where we might want to reach the proficiency cap. But, there are different play styles. Imperil + 5 phase; Imperil + max proficiency; No imperil + 5 phase; No imperil + max proficiency. Let's say that even for the scenarios without max proficiency, you have Lmax proficiency on non-proficiency staff, with 50 forge levels, ie. 0.31 proficiency factor or 8.6% mitigation reduction
The below calculations will be based on Cracker Jim having 60% Mmi and 72% holy mitigation. Now, I have no idea what Cracker Jim's real Mmi is, and not all mobs have such high holy mitigation. Also, reaching max proficiency probably means sacrificing 2 small pieces of phase which is ?? % of damage. Let's say damage output is reduced by 25%.
- Imperil + 5 phase gives -50% Mmi and -25% (-33.6% with proficiency) holy/dark mitigation. 10k base dmg would only leave only 10000*(1-0.6+0.5)*(1-0.72+.336)=5544dmg after mitigations.
- Imperil + max proficiency gives -50% Mmi and -25% (-75% with proficiency) holy/dark mitigation. 7.5k base dmg would leave 7500*(1-0.6+0.5)*(1-0.72+0.72)=6750dmg
- No imperil + 5 phase gives (-8.6% with proficiency) holy/dark mitigation. 10k base dmg would leave 10000*(1-0.6)*(1-0.72+0.086)=1464dmg
- No imperil + max proficiency gives (-50% with proficiency) holy/dark mitigation. 7.5k base dmg would leave 7500*(1-0.6)*(1-0.72+0.5)=2340dmg
On these assumptions, going for max proficiency has about the same absolute difference in dmg (~1000), but in relative terms it is more important when using Imperil than without Imperil. Also, Imperil makes so much difference in damage that spending 4 rounds of Imperil + 2 rounds of damage ~ 6 rounds of damage without Imperil.
I'm going to stop rambling now because reading too much into made up figures (Cracker Jim's Mmi) is probably not wise, and I'm not sure if this makes sense anymore.