10v10 Changes
Increase HP while lowering the effectiveness of healing. At the moment, if there are two competent healers on the same team it is nearly impossible to kill them short of a miracle. More HP would prevent being instantly killed by some players in 10v10, but not fully eliminating the possibility of dying within a CC.
The map needs to be changed - an easy map would be Dreadlore Laboratory or something similar. I don't think many players will remember this, but in the first iteration of Territory War there were spawn points for the guild defending the territory. If you were to pass a certain point (which was identified by some object) you would be instantly killed preventing you to go into their spawn. If a kill plane can be introduced to the team's spawn points to prevent the enemy team from entering the spawn/spawn camping this would be an easy way to fix the regrouping issue.
Life System needs to be introduced, I would say individual lives would be better but if a team has players that disconnect or alpaca during the fight they are automatically at a disadvantage. I'd suggest that each team is allotted 50 total lives to play with and introduce a set respawn timer, maybe every 30 or 45 seconds.
Match time should be reduced to either 4 minutes or 5 minutes. This time would be dependent on other changes (life system, hp, etc). If a life system is introduced, the team with the most remaining lives should be awarded the victory for the round. This could easily be abused as people could theoretically sit in spawn and not PvP, but that should easily be record-able and punishable.