In Mid Wars, on rare occasion the team that is winning will win by pushing towers and eventually bringing down the last structure. I say rare, because almost everyone backdoors the base and wins in almost all of the games. You've designed mid wars to be a fast paced game, but with backdooring the game quickly grinds to a halt as backdooring begins. The following begin to happen:
-Whole team guards Tree
-Teams just diving to destroy Tree
-1-2 people guard Tree and rest go get slaughtered meeting the other team's backdooring force, that later on is slaughtered by the reviving force
Game just goes back and forth without any purpose whatsoever, and without a clear victor. Till sometime past 60minute mark, someone gets lucky and backdoors successfully.
As a gamer, I enjoy all the action I can get but when things become repetitive (as described above) I get bored and I don't want to play Mid Wars again.
Backdooring is part of the game, but in mid wars backdooring needs to be more difficult:
1. Base tower and tree defense scales depending on units around it. When there are Legion creeps in 1000 unit radius of structure, that structure receives 100% of the damage. When no creeps are nearby the structure only receives 25% of the damage when 1 hero is hitting it, 35% when 2 are hitting it, 45% when 3 are hitting it, and 75% when 4 or more are hitting it.
2. The Legion creeps become much much much tougher to kill in late game. This way the team that is losing HAS to defend first before refocusing their efforts to backdoor the winning team's base.
3. Come up with better ways to make backdooring more difficult
Your suggestion means that not only do you have to win a team fight, you then have to push the creeps forward (a VERY slow process in mid wars). So if you win a fight at the river (or even slightly further forward), you still can't get to the shrine as you have to push the creeps forward. Meaning the enemy has respawned with full hp and mana while you have all the damage from the previous fight. It'd be so hard to get to the shrine with creeps and wipe them and then the shrine.
Especially with some heroes that just decimate the creep lines, leaving no creeps alive.
I think your solution is worse than the "problem", and I don't agree with the problem you have either.