So top guilds can already beat nightmare and brutal boss, and not all members can get in hits since bosses die to fast.  It's a matter of time until all other guilds catch up.  So now, what the game encourages for max rewards, is that we divide clans into a few heavy hitters and a few new players so everyone can get maximum number of hits for top chests in each tier.

This is a bad system, since it discourages progress.  You don't want to progress as a guild, since you tax all other members on the number of hits they can take on the boss.  A good player wants to join your guild, sorry, you do to much damage to clan boss.

Increasing the hit points of the bosses won't change much, it will hurt new guilds more then anything.   And there will not be a perfect hit point cap for all bosses, this will be constantly changing to new heroes, changes to game, etc....will be impossible to keep it balanced.

I posted this suggestion before, let the bosses go to negative hit points.  If a boss is defeated, he will be in "banished" state.  So you can do more damage to bring his hit points to negatives.  Every player in every guild can hit whatever boss they chose, will not be forced to rush hits.

Give players more freedom, everyone wins.

Give rewards on clan boss reset, if the boss was banished (brought to 0 or below hit points).

KappaBase