Shaman Slow/Dot/Melee.... till what level-ish?

[workbench]

Hey all, I have a twinked lvl 29 shaman (fungi, granite face grinder, high HP/AC items). I'm noticing my ability to solo facetank multiple mobs at once is going away. I noticed it in Guk near LGuk. My strategy is to pull one mob with slow, using poison dot and meleeing away. If I get an add, I root and backup.

My question is, how long does this strategy hold up? Is there a point at which root rotting becomes more effective? Pretty subjective I know but just wanting to understand your experience around this strategy.