do you actually believe not being able to solo a champ is a legitimate issue? not every character can take on everything. dexers being able to solo champs or hell even in a small group would mean that tamers could very likely solo them even with slayer shields because magery wouldnt be based on "type" just the melee damage. dexers have their place currently. even with slayer shields you are going to be forced into very specific archetypes to take on high level content which will make every build identical and boring.
offering resistance to spells makes the items too OP - it makes resisting spells a moot skill. theres no way slayer shields should also work on the damage caused by magic. you are asking for too much
Provo dexxers yes. However, eventhough tamers are better for PvM, that does not prevent me from runnig around on my bard.
even though tamers might be easier to run dexers get the benefit of plat statues from amibs and 7's. dexers should include provo dexers, peace dexers, pure dexers - why does the conversation have to relate to pure dexers? theres no such thing as a pure tamer or a pure mage
if you want to resist the spells a monster uses - get resisting spells. what about when you use a slayer shield and resisting spells? absolute magery immunity for a particular mob type?
so using the uo renaissance resisting spells calculator at 100 resist you generally have a 50% chance to resist spells (ebolt is 50% exactly) then you add the block chance of a slayer shield of your proposed 30 - 50%. you now have an 80 to 100% chance to resist spells from a specific beast how is this not OP?
i doubt they would change the formula for monsters.. but some mobs do have higher than 100 magery and the calculator wont go higher than 100