Either the third laser tower get replaced behind the artillery factory or the whole base should be laser towers, replace the cannon towers with lasers. with the creation of the siege troop command combo its too easy to kill base and bomb it.
games last very long because the base was too easy to defend (and still can be defended well). if you find it easy to destroy it, your team is much better than the other, and the game shouldnt compensate that.
The cannons also deal large gobs of splash damage, making it harder to attack the base with a heavy tank taking almost no damage from the lazer towers due to his heavy armour. I like the change
Initially when the base is fully intact it may be a bit hard to penetrate if defended well. But once there is some penetration, the other team falls rapidly. Maybe they should, you say, since they allowed their enemy to get to this point; it's their destiny. But i've had really good tank games before, where if the offending team couldn't maintain their momentum, the defenders had a chance to make a comeback because their foe didn't capitalise on a major advantage. This should be the case. It's like a fight. You knock your opponent to the ground but can't knock him out, you struggle and wear yourself out. He should get a chance to make a comeback at this point because you failed to win. It makes the game more interesting if there is a possibility to repel your enemy, this is what has made tanks fun in the past.
Also on another note, and i've been meaning to say this for ages; make it so you can't buy from the enemy base. All the stuff you need should be brought with you in your tank to the enemy. If you nuke the base and kill all enemies, you can simply buy mortar teams from their own factory while they are respawning, leading to an extremely rapid death for their building.
Considering that later in the game, respawn times become larger and larger, dying once can mean the death of your base because you aren't around to defend it, especially when people can earn money as they kill you in your base, and purchase a factory from your own building.