I don't see class stacking as the problem. Teams have been class stacking for years now. I also don't see premades being the problem entirely. Certain premades actually make the root of the problem more apparent. Balance is off, and frontlines has been shown very little love by the devs this expansion. I'm pretty positive that that too many people are dealing with getting stat checked from the AST LB. (lol) Those that already have BH5 are doing 60%+ dmg for the next 15 seconds when AST LBs, 80% for the first 5 seconds. Those that are benefitting from the 50% dmg reduction from the frontline adjustments are now getting 60% for the next 15 seconds from the LB, 80% for the first 5 seconds. The reward for doing well while having an AST on the team is to go into the next fight as a group of tanky ADCs/APCs for your alliance...(I'm currently crying in tears due to laughter. The imagination on paper is real, and it may be a while before I'm able to clear my head of this. xD)

Frontlines really needs some deep love and actual thoughtful adjustments. You don't need to do anything about class stacking, because it'll always be there. You already went through SMN stacking, melee stacking, DRK stacking, SCH stacking...god forbid BRD and RDM stacking comes next after this, because everyone will be crying about nerfs for those. (Please don't get any ideas...) Just watch those stats. If it's taking only one class on top of certain mechanics and classes to push a team up to a possible 80% atk increase and/or a 80% def increase there's a problem.