I'll only believe that they've released Heart of fear too soon if we end up with another Icecrown Citadel / Dragon Soul situation where we get stuck with 1 raid for a longer than usual patch cycle..... If that happens then with hindsight i'd agree that Heart of fear has been released too soon.
If we are going to get left with 1 raid for more than 7-8 months before the next expansion then it would have made more sense to delay these raid releases for a bit longer.... But if they had done this then you'd get loads of threads complaining about how few raid bosses MOP has at release compared to previous expansion and how this shows that blizzard is lazy, doesn't care about the game anymore and has all it's best devs working on Titan.