WoW has existed before 5.2 too, and I'm not sure I'd even want to be in someone's guild who thinks that progress in HC ToT is an absolute meter of individual raider's skill.
Correct but there is no way to know if a player is good or not without raiding with them. If someone has multiple heroic kills of the current tier, they are far more likely to be good than the player who apped with no heroic kills. Is it Gospel and should you take it as 100%? Nope. BUT if I had to choose between someone with 7 heroic kills and someone with 1, all other things being roughly equal, im taking the 7 heroic guy every time.
As for OP, do it. There is a massive shortage of good players. If you can show you know your class and have some decent logs to back it up, your going to find a place somewhere. I would bet the vast majority of people in 13/13 guilds were once in a situation similar to yourself.