I don't think there should be 'duel pots' it should be as is, magic focused or stamina focused.
My biggest issue atm is with the looks, all pots of the same style look the same, ie Invulnerability potions with different secondary effects all look like the same red bottle which means sometimes you use the wrong one.
If the effect excist, it should be possible to be mixed with 2 other effects.
Wether anyone would use these or not is a different story, but I'd like to have the possibility.
ps. Give us potion that has heffect: Restore heath, Stun, Restore magicka and name it "Essence of Health" like every other health potions. Then we can start selling these for tanks. They will be in for a surprise!
The only one I really want to see is a magical version of speed/immovable/stamina pot. Would be nice for us slow magdks who have to be up in stamina players face and they can just dance around us.