Problem: The buff for having two altars is too powerful. The game becomes more winning early game and camping the other teams jungle to get their altar. Once you have both altars, it makes it way easier for the team that's already ahead to stay ahead.
Problem: The Vilemaw just hangs out most games, and some games teams don't even bother to go for him since he takes so long to kill and its so obvious when you are going for him. He's a really cool new addition to the map, but the buff and the gold aren't so good as to make him a high priority, the buff from having two altars is easier to get and more powerful. Also, since he's so hard to take down, requiring at least two team members, he's very risky to attack.
Solution: Switch the buff you get from killing Vilemaw and having two altars, increasing the value of killing Vilemaw and decreasing the potency of having both altars, if just slightly. Also, bump the gold for killing him back up to 280. These two changes would make the game much more balanced with an easy fix.