I've found myself using newer classes/constants/methods etc. in my addons, as I don't realise they're new.
So, I suggest that a since part is added to the phpdoc of the classes/methods/constants telling us the version of XenForo that it was added.
I know it would be a pain going back and adding it in, so maybe just for new ones now? I realise this is unlikely to be added in to the source, but I thought to suggest it anyway