Second wind is a recuperate that ticks just as hard, but 3x as often. It only procs when below 35%. It does not require combo points. It does not cost energy. It does not cost you a finisher. It does not cost you a GCD. It never falls off. Whereas a rogue takes at least five GCDs to build up his combo points to get a full recup off, sacrificing a damaging ability for self-healing, a warrior gets it for free.