Your counterargument falls apart when you start reading it. For rainbow builds "Sometimes stronger" Means "other times NOT stronger". Not stronger at other times means the dual element builds are also "sometimes stronger" and going by your logic dual element builds are stronger. What utility? Rainbow builds have decent utility in everything. A bit of speed, a touch of poison, a mite of lifesteal. Wheras a build with dual elements has a ton of utility, just not so widespread. You can fight Quira with your rainbow friends, but it would be better to have several dual elemental friends - they are each much more specialized and together they cover each other's weaknesses with a power far stronger than the coverage a rainbow build can give in that element. Maybe rainbow builds are stronger for solo players but you cannot ignore those that play together - most hard quests were meant to require more than one player. Just because you can survive one of those battles doesn't mean you did it as quickly as a more specialized player could have. Let's look at Agility. That player can have up to an 80.5% chance to take zero damage from any damage source including other elements. So by specializing in agility they are as invincible as you claim rainbow builds to be. But this is only half of that player's skill points. They still have up to 100 skill points that they can put into any other element! The only time a rainbow build will truly be more powerful than a dual element build would be with the right rainbow mythics or if the dual elemental set involves defense (because defense is nearly useless since it has no effect on elemental damage).