Whilst RiftRunner has do defined classes, you can define your own by selecting the skills and attributes you want. Warriors, Wizards, Clerics and Thieves still apply. It's just how you make them.

Perhaps they should increase the requirements for armour further. If you make Plate Mail armour require 100 Strength to don, then a wizard won't be able to because they'll be pumping attribute points into Intelligence. But they might have a chance with Chain or Mithril armour.

Perhaps armour could also affect your reaction time, regardless of class. Until you excede an Armour's requirement by 50%, all of your actions are slowed by wearing it, including movement and combat. But how do you work this out with five separate pieces of armour (body, legs, feet, hands and head)?