I thought the Valeyard was the Doctor in some mid-regeneration process or something? I was never entirely clear on that, though, and I think the writers weren't, either. This was befoer a lot of the show's "rules" had been established.
Whiiiiiich gets me back to an issue with Moffat.
Storytelling requires convincing universe-building. The setting of your story needs to be understandable and believable, even if it's fantastical in nature. For audiences to take a storyteller seriously, that means the storyteller must obey the rules of the universe he or she creates...OR, if the storyteller is going to break those rules, the storyteller must explain how and why the rules were broken (which, in and of itself, often creates a new rule).
So, it gets established that the Time Lords get 13 regenerations before they die. Super. We have a rule. 13 deaths and then you're done.
Later, it gets established that the Time Lords can grant additional regenerations. No problem. We're breaking or adding on to the previous rule. You get 13...unless you're given more. For this reason, I don't fault Moffat for his "The Time Lords escaped one universe and granted the Doctor additional regenerations from a different universe" dodge on the 13 regenerations issue. There was already a "rule" for that. The only addition that Moffat made was "...and they can do it from anywhere in space or time or even different universes." Cool. Rules still intact, mostly.
Where I take issue with Moffat is when he either ignores his own rules, or claims they don't matter. The Statue of Liberty is not made of stone, so how can it be a Weeping Angel? For that matter, given how Weeping Angels can't move when in anyone's line of sight, having one be a building-sized statue makes literally no sense because, presumably, they'd ALWAYS be in someone's line of sight. Moffat, though, just ignores that because hey, it looks cool.
Likewise, he does a bit where the Doctor produces a cup of tea out of thin air and somehow makes it disappear later. Or rather, it simply never appears later. His answer to this is "It's Doctor Who. Just accept it."
The problem with this attitude is that it's basically just a dodge for lazy, ****ty writing. Often, this is done purely in service of what's supposed to be a "cool" moment, which serves no purpose beyond looking "cool." The problem is that it doesn't look cool, at least not to me. Instead, it just looks lazy and immature. It's this stuff that makes me think "Fan fiction." Fan fiction has a reputation for wish fulfillment and a propensity to indulge in "cool" for its own sake, rather than in service to the story. Moffat ****ing LOVES doing this, and it is, to me, what makes his writing come across as amateurish.
The really irritating aspect, though, is that he's capable of so much more. When he's reined in, when he doesn't have unlimited ability to do whatever the hell he wants, he ends up producing really solid, moving, insightful science fiction with compelling characters. But left unfettered, he's indulgent, lazy, and obnoxious.