Nerfing towers isn't the best solution to the current meta. The reason they work so well together is because Dartling, Ninja, Farm, Hero have fantastic synergy. Neither are individually OP (in my opinion), so a nerf to them would also nerf other strategies. So it's not that towers need to be nerfed, it's that tower synergy needs to be nerfed.

The way to avoid that is to add a tower/hero ban option pre-game (most likely a screen before the hero menu so you can ban heroes. It would be unfair to see your opponent choose Striker and then ban bomb when you know damn well that's what strategy your opponent will be going for).

This can be added similar to how the more difficult maps were added in the higher arenas - add this tower ban feature to the game in ZOMG and HOM.

Not only would this basically eliminate metas at the highest level because players will have to know varieties of strategies in case of tower bans, but it would also create more fun, high-level gameplay with those other strategies. Instead of mastering one, you have to master many different strategies. Plus, it will force players to continue to be creative in discovering newer ones as well.

All in all, this is easily the best fix to the current meta and honestly all future metas of the game.