Ask anyone who leveled a 
Warrior in the original game: the problem wasn't damage, it was eating after every fight. Forever's two baseline changes go straight at that.
Victory Rush at 20
Kill an enemy that's worth experience and you get Victory Rush: an instant strike that heals you for 10% of your maximum health (30-second cooldown). On a normal questing pull, that's most of the damage you took coming back for free. Use it right after every kill.
Tactical Mastery at 14
You keep 10 Rage when you change stance. Opening in Battle Stance and switching to Defensive when a fight goes wrong no longer means starting from zero.
Rage changes
Rage from hitting now scales with weapon speed, and crits give 100% more. So a slow two-handed weapon is even more important than before. Rage from taking damage ignores absorbs.
Where it ranks
Better, not best. We still rank it B for solo leveling in the leveling tier list, because a bad weapon or a three-enemy pull can still end badly. With a healer friend, it's one of the fastest. The Warrior leveling guide covers the rest.