Guild Wars 2

• make the stack of condition to do less damage the more there are for the same condition. for example up to 5 stacks of burning the damage 100% but after that the player receive less and less damage from additional stacks. Everybody is still doing damage = bags for the kill, still the damage is normalized so it doesn’t get crazy. Some weak conditions (like bleed) could have more stacks at 100 than other more bursty (like fire). Because it’s a percentage of the total damage from the stack condition damage stat still matters.

• conditions do 33% damage first tick and 66% second tick, and 100% third and following. This is meant to give enough time to the player to handle the cleanses in case of a Epi bomb. It gets 2 seconds to react still gets damage for the attack.

or just run proper builds and group comp.

• Make Epidemic blockable. This doesn’t affect PvE at all.
• Give Epidemic a highly visible tell overhead (so it can be seen in the midst of battle) as soon as the Necromancer starts casting. This gives the target 1 second to react and dodge.

Done. You’ve balanced Epidemic and added counterplay without adversely affecting PvE.