That's how I felt at first, honestly, but I've been proven wrong about the fact. The point isn't to use them for damage. It's to use them for movement. You can use one movement skill to charge in, do a Hundred Blades if there's time, and then use the other movement skill to get out. The whirl attack counts as an evasion skill, so it's extremely good for escape, and it's the primary reason why solo Lupus kills were able to be done at all with a Warrior. The rush skill covers a whole lot of range, so it's extremely effective at putting some distance between you and the enemy team. Then there's the fact that you have a trait that breaks immobilize with movement skills, and then you have something that's almost exactly like the warhorn cleansing trait when it comes to getting away. You can add the fact that everyone who mains Greatsword uses their weapon switch for either offhand Shield for defense or offhand Warhorn for escape, and if it's Warhorn they'll have a 5 second weapon swap time so they can keep that swiftness up to extend the distance of their Greatsword movement skills. Oh, and the whirl is extremely good for building up adrenaline while staying on the move. And the whirl attack had to have it's damage nerfed at one point, but the rush attack can still hit decently hard in a high power/crit damage build.
That turned long winded. What I'm trying to get at is that the Greatsword hits hard, and it's the best movement weapon set on par with Sword/Warhorn, which many Warriors using Greatsword keep as their weapon swap/extra getaway option anyway. It's precious, because things hit too damn hard in this game much of the time and the only way to survive is to completely negate or getaway from damage at times, and the Greatsword facilitates that.
As for movement skills in general, what's probably going to become a problem eventually is that skills meant to be gap-closers are way too good at being gap-openers instead.