The tower buff is actually a nerf that aids snowballing.

Minions deal more dmg to towers now. A couple hundred hp is but a small buffer. Which for one means they deal more chunk dmg if you are forced under tower during lane phase.

Minions take less and deal more dmg if your team has a higher total lvl. Killing people gives xp. Getting killed costs you time to get xp. Minions deal even more dmg if your team has 3 levels more and taken 2 more turrets than the opposing team. Source: http://leagueoflegends.wikia.com/wiki/Minion

This means that splitpushing is no longer needed for teams that are ahead. The minions will autopush, and take turrets faster now. Teams that are behind need to spend resources to deal with minion waves, while teams that are ahead can 5 man force whatever they want.

What strategy is left if you can brute force push mid off a small lead and win?