I would very like to see more boss mechanics which encourage party play rather than the full out dps down style or the tank and spank style we have now. Forgot which thread I wrote my ideas previously, but roughly the mechanics below will work nicely in ToS.
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Periodically the boss will hand out a 6secs debuff to a random player within the area. Player with the debuff will damage all other players surrounding him/her if he doesn’t move away from others, damage is around 3-4k damage per tick that ignores mdef. This debuff cannot be removed and will last for a full 6 secs. Player with the debuff wouldn’t take any damage from it at all.
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Boss will root himself/herself and summon a group of 10-20 minions (with 1-2m hp each) that will make a beeline to the boss. The minions move slowly, ignores any threat or CCs and only prioritise in getting to the boss. Players will have to dps down the minions once they see them. Each minon that successfully reaches the boss will heal the boss by 5% hp.
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Environment mechanics for bosses. Some bosses require the team to split to operate on interact’able objects to remove the boss’s invincible shield
Something along these lines, the purpose is to let the boss fight be more of a team coordination/play effort than just everyone spamming all their skills whenever it is off cooldown. There should be some back and forth, when to and not to dps, when to focus and not to focus on boss and when to split or focus on objective/sub-objectives. All these make the boss fight more interactive.

