Dismantle and Rend Mind you really should be using. Even if you don't want to learn the mechanics and throw them up when it's able to lower a major attack, you should at least throw Dismantle, (or Rend Mind if you know it's a fully magic damage based enemy), in every now and then between your normal attacks when you don't have any oGCDs to hit with, since it doesn't hurt your damage and makes the tank take a little bit less damage from attacks from a bit. 5% may not sound like much, but it adds up pretty quickly.....
As for Grenado Shot, I can get, but don't agree with entirely. There's a time and place for it, namely when dealing with weak mobs that will die quickly, or when dealing with a particularly large group of adds. That extra 20 damage may not be a whole lot, but again, small-seeming numbers can add up.....
On the other three I completely agree, and below are my reasons why.....
Leg Graze - Doesn't do any damage, and is virtually useless in group content due to the fact that enemies won't be moving once the tank stops. It's only real use is to slow down a single enemy chasing you if the tank dies, in which case you probably need more than that to save you. In solo content, it's slightly more usable pre-GB since you can use it to slow an enemy while you run around, keeping you from getting hit. Still not worth a hot bar slot though.....
Foot Graze - Only slightly better than Leg Graze, since again, enemies won't be moving in group content once the tank stops. It CAN be used to hold back an enemy if for some reason it's necessary, or if you use a Blank combo to sit an enemy out of a fight. That's still inadvisable though due to the fact that being kept away from the group means AoEs can't hit that enemy, and the tank can't build aggro on it. Also, like all bind skills, a single hit will break the bind, so an AoE or ranged player hitting the enemy right as you use it means that it was a waste of a skill. More useful in Solo content because you can lower the number of enemies attacking you by using it, which helps slightly with our lack of self-healing or defensive skills. Still really not worth a hot bar slot by any means though....
Suppressive Fire - I'll go ahead and say it. Outside of solo content or having a tank who refuses to stun, this skill is completely useless. You have to be point blank range to use it, enemies have a limit to the number of times they can be stunned so you run the risk of hitting that limit on bosses preventing the tank from stopping dangerous attacks, and shares a cooldown with Head Graze which does the same damage, has vastly superior range, and has no limit on the number of times its effect can work on the target. Again, if your tank is stunning, or you have NIN/MNK/DRG/WHM/AST in the party, then you have no reason to ever use this skill. In solo content, it is what it is, a stun, which is useful if you can't dodge an attack. Again though, not worth having on the hotbar.....
As you can see, these three skills aren't really useless, they're just so close to useless in group content that you'll never be using them outside of VERY specific situations. Because of this, it's better to just leave them off the hotbar and pretend they don't exist unless you find some piece of solo content you can't do without them. They might have some use in PvP as well, but that's more or less solo content anyhow because of how it's set up and since other players don't follow the same mentality that NPC monsters do, (usually anyhow)....