I'm not sure if it's too late, but I know that not all skills are immediately introduced, so if you have the time--
I was thinking about a skill today that may be used with the Rogue class. This skill would basically involve buffing the Rogue's (or maybe Warrior's) speed significantly and the armor a tad bit. This skill could be used for breaking the line of battle or performing a "blitzkrieg". Imagine 2 or 3 rogues all running in and out of range rapidly while dealing damage. Immediately, this sounds OP. However, this buff would decrease the damage of the caster, as well as make the caster very immune to basic comboes. A mega combo would mean instant death.
Not only would this improve basic tactics and teamwork in PVE, it would also positively affect PVP in the same way. PVP may involve real strategy, and thus, real skill.