Can someone give me an in-depth explanation why Summoner is arguably the worst DPS?

[Xisin]

Those numbers are off, you are (and I just mathed it myself) ignoring ice phase. I honestly challenge any blm on here to beat a good summoner without using firestarters and thunderclouds.

170 * 1.8 = 306
306/2.3 = 133.04
That is blms 600-700 dps fire phase you are mathing. (that dps is including an adequate amount of procs.)

Let's look at ice phase.

Blizz 3 240 potency @ Af 3 = 240 *.7 = 168 (gcd is still 2.3 in this example)
168/2.3 = 73.04

Blizz 1 @ 170 potency = 170/2.3 = 73.91

Thunder 1/2 (lets do T1 since you know its the most common) 30 potency on application 40 per tick for 12 seconds (so on cast 30 potency 30/2.3 =13.04) overtime duration = 160 potency + 30 on initial = 190 potency which adds up to 190/2.3 =82.6 potency for thunder TOTAL.)

finally fire 3 with UI3 = 240 potency with UI (its the same as AF3 Blizzz) it has gcd on it too so the cast time is moot other than just for the sake of making sure the spell resolves.) =73.04 potency

adding this up:

73.04+73.91+82.6+73.04=302.59 potency over the course of 9.2 seconds so 75.64 potency per second in ice phase. quite good no? (this is including thunder ticks during fire phase, it's lower if you calculate impact damage only.)

Fire phase is 133 potency per second for ATLEAST 5 gcds.

so forsaking procs altogether

we have 133 potency per second for 2.3 * 5 seconds (11.5 seconds)
and 75.64 potency per second for 3-4 gcds (6.9 minimum, 9.2 max) (AGAIN I cannot stress this enough, this is including the thunder ticks during fire phase.)

it's safe to say those numbers are off, and that the ice phase was overlooked in those calculations.

Again spell speed is the biggest offender.