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Probably the developers have sensed this flaw, so they added a huge resist boost with dimensions. They did add will crystal bonus too, but to a less extent. Right now, my resists looks like this (see to the left) with Hades equipped. I have 5 electro dimensions (1 advanced, 3 intermediate and one basic). If we suppose the strong players have a similar reduce resist like me, then their Hercules deals 62% less damage on me. (see here how resist damage reduction is calculated.) Also you can see that I don't bother having a significant secondary and tertiary resistance. Couldn't make them as high as 870 anyway, so in pvp they wouldn't help. In pvp (sky trial, god's descent), I just convert my best crystals to the proper element when necessary.
So with dimensions, resistance finally became a useful stat. And it is an important tactical element which dimensions you do. With this super-high resistance, I was able to kill God's descent boss 29 - with one attempt - AFK!!
And resist is now important in PVP - in battleground, I could kill R4GE, while he had more than 100k advantage in BR:
(And this is not a boasting - I have maximum respect for the live player behind the ToK NM shadow - it's just an example what resist can do now.)
So, be careful what dimensions you do. I seem to find a lot more dimensions than I use, so I can select. I was lucky to get a lot of electro and keep getting more, so I will stick around with that for a while. Although Hercules is the most common sylph, people will change tactic eventually. Going heavy-dark is another option, for a mage, it is a must if you want to be good in Class Wars. I really like when in a game, tactics becomes important, and its no longer just a who-have-the-higher BR competiton.