I've said time and time again that shammy is gear dependent and this is one of the reasons for it. Your melee damage sucks, and unless you plan on getting a weapon that procs a decent DD or DoT (barb spiritist's hammer or blight, hammer of the scourge) you won't be doing much damage with auto attack on. The kicker, though, is that you're not meant to and you don't really have to. Shammy tanking with a slowed mob is used to maintain 100% DoT damage on a mob that won't be running or moving because it's busy trying to put you on the ground, but with a 70% slow and incapacitate/malise you should be able to take a quite a few hits before it goes down from DoT and pet DPS. You should steer away from shammy tanking until level 34 (pet) or 39 (best slow) if you can't manage buying the lvl 30 proc weapons (barb hammer/blight).
In full rune-etched and ~230 dex after pot I take down seafuries with practically zero downtime and absolutely no sitting down to med thru rage/chloro/cannibalize. Pull with slow, sick the pet and barb hammer it down. These things have ~5k hp and hit for near 80 double, but the HP i lose from damage is less than the health i chew up via cannibalize. Once you've equipped yourself fairly well you can even off-tank slowed planar mobs (minus posky, really) and then it starts to feel like a real shaman again
[You must be logged in to view images. Log in or Register.]