Looking at new Monk vids i125+ with single target numbers in the low 600's (very nice) it shows that the rate at which SMN damage increases is low.
I would attribute it to the stat weights more than gear and/or MP conservation especially against Melee classes.
Given SMN's low Magic Damage weight 6.57 (20-40% lower than other classes) and the rate that secondary stats increase 7-10% per 10 iLvls there is a stat scaling balance issue.
At low iLvl's where the secondary stats started relatively high compared to Weapon/Main stats, SMN did competitively well. But due to the rate that the main stats increase VS secondary stats, and how SMN skill potency was balanced against other classes on release, each update in gear will see a reduced increase in SMN damage.
Comparison to BLM
@ ~3 MD per 10 iLVL's BLM will accelerate past SMN at a Rate of 4 INT per MD. This doesn't include the low Secondary stat gain on SMN, especially Spell Speed.
i135 Weapon
BLM 656 Main Hand value - INT
SMN 539 Main Hand value - INT
Difference 117 INT
i70 Weapon
BLM 504 Main Hand Value - INT
SMN 413 Main Hand Value - INT
Difference 91 INT
The newest set of gear makes this very noticeable due to the amount of Spell Speed on the mage gear and how it scales with Summoner Damage. I haven't done the math but given BLM VS SMN BiS + the difference on scaling with WD/secondary stats we are probably looking at a difference of 40-60 INT. ~10% + on gear alone.
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I can see why they would take this approach since currently the pet scales off WD and INT at a higher rate than SMN (almost double, but it doesn't scale off Secondary Stats as a trade off) but the lesser increase on secondary stats causes SMN to fall behind. This appears to be an attempt to balance the Ratio of SMN to Pet damage on top of balancing SMN to all other classes.
My only guess to balance this would be to increase the damage scaling of pets from MD/INT (eventually pets will become a high % of overall SMN Damage though)
OR
Boost the weight of secondary stats for summoner - not ideal due to the non-static nature of gear secondary stats
OR
Most ideal IMO - Increase the Weight of MD for SMN and have the pet scale the same as SMN for all stats, including Spell Speed. In order to balance Magic Pets VS Melee pets, have DET scale the same way as it does for Melee and AA Damage.
I.E. - Garuda 2.4 GCD VS Ifrit 2.4 GCD for Flame Crush + DET Bonus for AA Damage, since AA doesn't scale off Spell Speed/Skill Speed
(to prevent SS from being too ideal for the use of Garuda over Ifrit)
This would just make pet damage an extension of the SMN (balanced as Raw Potency) instead of having to balance the pet on top of how the SMN performs. I.E. (A + B = C instead of A + B^2-(D+F))
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Because of this, I don't think SMN damage is being effected by a single issue.
It appears to be a combination of
- Gear/Stat Weights
- MP Management in long fights
I'm not convinced that MP management is the main issue that is reducing SMN potential over other classes, but rather a by-product of players trying to push every ounce of damage out of it to remain competitive with other classes. (Fester VS Energy Drain is such a miniscule portion of overall damage)
Patching SMN with potency increases will not address the gear scaling issues compared to other classes.
Increasing MP recovery/reducing spell cost will not address the damage difference to other classes approaching ilvl 131
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Does this mean that SMN is not good in current endgame content? No. But it does take a highly skilled SMN to push high enough numbers to compete with currently average players of other DPS classes (not including Bard).
Dummy Comparison iLVL 131
Estimated (Edited to bring DPS values to a less simulated amount)
SMN Single Target Damage @ i131 - 525 DPS (390 SMN + 135 PET) - Garuda
Melee 625
BRD 540
BLM 585
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Final Thoughts
Increase Summoner MD weight to around 7.5 - reduce how much the pet is effected by MD and INT and allow them to be effected by secondary stats.