Cleave is one of my most used powers. Arguably a favorite in terms of "what do I want to use?" That's because it's simple and effective. As long as you fight with a melee/thrown weapon, it's your best and most easily accessible form of crowd damage, and it deals a good amount (assuming you have an actual build). Unfortunately, despite how much I like and use it, it is also the source of my gripe. It is, quite simply, too good. Unless you're fighting solo foes, and know that you're going to be fighting a solo enemy, Cleave is pretty much guaranteed a spot in your active arsenal. Even at higher levels, the only Warrior skill which deals physical damage to multiple enemies at once is the Warrior's ultimate
Look at the other level 2 Warrior abilities. You have Dominance and Warcry. I have never used them, because they don't seem worth the slot. With Warcry, you want sexiness to be able to land a hit (a stat more tied with light armor and Presence, whereas a Warrior is supposed to use heavy armor for their level one passive, and while presence would be useful for beefing up companions as a tank, a warrior tends to dish out lots of attacks and plans to take lots of attacks, so you want strength to deal damage, toughness to tank hits, and agility to both land hits and not take as many hits), and even aside from that it only draws threat, deals 10 resolve damage (something warriors tend not to target, so this is presumably to draw additional threat), and applies terrified. Terrified reduces mental resistance and sexiness. So, you know what this does for a Warrior's playstyle? It doesn't. It's basically just a charmer ability that lost most of its resolve damage but still generates the threat it would have gained with that damage. Terrified's mental resistance drop is only useful for if you want to boost resolve damage, something which is primarily the focus of charmers rather than warriors, and as for the threat buildup, well, just use cleave. You'll gain a lot of threat if you just deal a huge chunk of damage, especially with Guarded stance up.
As for Dominance, it is useful, as long as you're using a shield. Because with a shield, you're probably using a one-handed weapon, and one-handers without a dual-wielded partner aren't particularly great. With a warrior with a curved sword, I found that Dominance was definitely outdamaging the basic attack, by roughly 2x. The problem, however, is that Rend exists. That character was dealing just as much damage with Rend and Dominance, and that got much worse when I swapped over to a Pike. Dominance's damage remains the same, regardless of weapon, since it's a non-weapon melee attack, so when I was using the pike, the basic attacks were nearly on par with Dominance, and Rend was vastly overpowering Dominance. And not only that, but Rend applies a damage over time effect which brings the total damage above Dominance for even the curved sword, and Rend is only a 2-turn cooldown, whereas Dominance is a 4-turn cooldown. Dominance's only extra effect beyond being an unarmed melee attack is that it generates high threat. In team fights, Dominance is not worth using over cleave because, again, just hit them for a ton of damage if you want to build up threat. In solos, then Dominance would be a strong threat tool, but otherwise you can just use Rend and severely outclass it in damage and cooldown. It also inflicts aroused, but, well, you're a warrior, not a charmer or spellcaster. Arousal only decreases the targets magical damage and defense, and unlike Warcry the arousal is single-target. If your foes isn't a spellcaster either, there's not really much point. The real kicker is that, at level 6, a Warrior can get Bull Rush, A.K.A. the better Dominance. It does much more damage, knocks the target prone (A stun is often more useful than a debuff to magical resistance for a physical fighter, or even for the team as a whole), and it claims to have "massive threat" rather than "high threat." The only downside is that it's encounter only, but a recharge of four turns is quite large, such that most encounters tend to go for a shorter amount of time. Plus, the primary intended effect of generating a ton of threat shouldn't be that necessary to reactivate later, assuming you have a threat-based At Will and have been consistently dealing damage.
TL;DR: The problem with Cleave is that it's an extremely useful and widespread tool, whereas its peers are down in the dumps abilities which are outclassed by so many others and which would feel massively out of place in terms of effect if it weren't for the threat generation, but threat is already generated through doing tons of damage so you might as well just use Cleave anyways, outside of the scripted one-on-one bosses.