I think you're misunderstanding. It's not so much that the deck is too good. It isn't. But the deck's redundancy re: the infinite life combo is doing a lot of very weird things to the format. People are reacting to it by playing decks that can go around it (Tron, via Karn/Mindslaver), avoid it entirely (Mill), or just go over the top of it completely (Splinter Twin.) This is resulting in the push towards combo combo all the time- where even the aggro and control decks are implementing combo finishes while linear aggro like Affinity and G/R just falls by the wayside.
I have to disagree. Linear aggro decks like Affinity are poorly equipped to deal with melira pod, but it has absolutely nothing to do with the infinite life combo -- it's because midrange decks containing recurring lifegain spells beat aggro. Have you played these matchups? Melira pod is unique, and there is a lot of discussion of its place in the metagame, but it isn't the infinite life combo that's pushing aggro out of the format at all. It's the fact that the format-defining deck has an early board presence, a ton of flexibility, the ability to repeatedly gain life, and an immensely powerful midrange strategy available in persist+township.
The infinite life combo has far less to do with aggro's decline than the fact that melira-pod is naturally
insane against aggressive strategies.
Infinite lifegain is one trick melira-pod is capable of, and not its main goal. The deck is fantastic, but not dominant -- only 9-12% of the MTGO metagame right now, with some sites reporting it as less common than american midrange.
This trick won't occur every game, or every match, or even every other match. It's very easily hated and entirely unnecessary to win. The metagame didn't shift because of the combo -- it shifted because melirapod is good.
Honestly, I think the banning of Bloodbraid Elf was the real catalyst in the massive metagame shift. Jund, a deck running a large amount of disruption and maindecked graveyard hate in DRS, no longer has the ability to punish control strategies with a hasted beater, or blow open midrange mirrors with the ridiculous card advantage BBE provided. The metagame is still developing with the neutering of a dominant deck, and it's very difficult to predict where it will go. Melirapod may be considered format-defining, and it's a large enough portion of the metagame that you MUST consider it when you choose a deck, but claiming that one of its secondary goals is what's shifting the metagame towards combo isn't really logical.
When Jund was dominant, melira pod was not a deck, depsite having the same tools available. The metagame was definitely focused around beating jund, which was unhealthy.
Here's my theory:
Now that things have opened up a lot more, with a large percentage of the metagame on MTGO being considered "rogue" due to the obscene number of options available, combo becomes viable again as a way to pick on decks that play fair. As a result, people have to start running permission and disruption in the main, leading to control/midrange strategies like RWU. Those, in turn, are beaten by decks that focus more on ramp/control such as mono-U tron. Melira-pod exists as a powerful midrange strategy capable of pretending to be an aggro deck -- its flexibility gives it a reasonable matchup against almost every deck in the field, but isn't dominant. It's our 'fair' deck.
