playing a shaman isn't about doing significant damage with your dots. daoc is a game where by design, not all classes can do everything. In some games, there are different specs for every class that allow them to dps/heal/tank, but not daoc. Your role in fights (which is one of the most important roles) is to shear/disease/root etc.
By comparison, a wizzy's role is to blow things up as quickly as possible. They pay for this in the way of extremely low survivability, and low health etc. Nearly any class will die to two wizzies free casting on them for 3+ casts each, which is the way that it should be.
I can see why you would think resists aren't doing much for you, but look at it closer. The wizzy surely has 10% spellpierce, so there your resists start at 40%. If they used traldor's charge, there is another 5% pierce, bringing out to 35% resists. Throw on top of this their debuff, and your resists are down to 20% - lower than a good template's base resists (if you have ever been hit by nukes while you had sub par resists you will know how badly it can hurt). You can see how quickly your resists disappear. Then, add in depending on relics 10% or 20% to their damage, and you can see why they hit so hard. Just imagine if you only had 26% resists, then would basically be nuking you as if you were naked. Believe me, the resists do alot even if it doesn't seem like it.
Also keep in mind there are different tiers of resists. Getting RA's such as AoM and EM can increase your resists in other tiers, which can help when you are getting bursted down.
How much damage you do/receive is all about how you character is set up, shamen have the unique ability to set themselves up in so many ways (be it damage, survivability, healing etc) you just need to find what works best for you. That being said, anytime 2x+ casters are free casting on your for more than 1 cast you ARE going to die, resists just give you a few more seconds to try to los/get out of range/interrupt
Hope this helps at all
-Holy
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Holydott - 51 / RR9 / Shaman
Loaded / Igraine / Midgard