I have my own doubts about his top level, but I'd never rule someone out because of past experiences if they're playing well and showing positive signs. We have a grand history of players coming through late career after struggles to be fair. I think it's probably good to assume others capable of learning and growth. I haven't a clue what kind of player he was back then if it suited the SPL or that Hearts team, and if this version is any better. He did make 42 apps in 1 and a half seasons, so he wasn't exactly unused either.
Footballer's careers aren't static things. You'd hope at 28 he is around his prime and is in fact better, fit and playing with confidence. He's in Ireland because his family was homesick and didn't like living in the US from what I gather, so he's not in the LOI as of some sort of punishment for being a failure.
He's been wildly inconsistent for Pat's, but the version of him we've seen the past 2 months is probably the best and most consistent he has been in his 2 years at home, his set pieces are a weapon, if that domestic based squad ever got off the ground, I'd love to see how players like him fared.