This strategy has obvious weaknesses.
Once the idols summons die they can't resummon. So aoe them down! Each time you kill one, they have effectively lost gold.
There is a cooldown between idol summoning so they have to spend alot of time at the crystal, use this to get a level advantage.
The player is investing all their gold in idols, that means they will have very low hp and armour, you need to exploit this. Yes they're very powerful in the early levels, but you just have to play defensively, hug your tower! They won't be able to push if you're there next to it. So if you can avoid dying and limit their pushing power, once you get to levels 5-7, you'll have the damage to focus fire them down, so work with your team to do this and each time they die they will lose thousands of gold and have to spend minutes resummoning.
I've gone up against this a number of times against a variety of generals, we just tried to limit their pushing, and look for ganks. Once we'd killed the DG once or twice, they'd wasted so much gold and time that we had a definite advantage, and went on to take easy wins. Just don't try and 1vs1 them early on, it is what they want you to do.
