Summoner Cross Skills/Rotation?

[PriyaJugulataris]

I agree with you on everything but how you explained rotation.
Wait for DOTS to almost fall off before using contagion, fester like said and whenever you can when all 3 dots are up.
I would use ruin I, simply due to the fact its double MP for same damage, the insta cast is ok, but after one cast you wont be casting any faster than ruin I.
Your aim is to keep all of your DOTs up, and use contagion to extend the ones you cast with raging strikes.

The reason I used Ruin II in the initial rotation is to fit all skills under the RS duration (Weaving OGCD and GCD's is important yo)
Contagion adds the same amount of time regardless of when, but if you use it right after a fresh application, you have the advantage of possibly baning it on to other targets.
Contagion's CD is far shorter than RS, so you can and should use it even when RS isn't up as it boosts your DPS.