Well, Comparing...
I would have to say that half-orcs are at least a little underpowered, even in their niche, compared to a dwarf.
For the fighter class, dwarves are flat out just better. Their only real penalty is neutralized by the fact that they don't take movement penalties for heavy armour or carrying a heavy load, and most people in this profession take full plate. Then, for abilities, the half-orc has +2 str, -2 int, while the dwarf has +2 con... Some might argue that the -2 int isn't important, but unless you are making your orc extremely stupid (in which case, the player was probably more likely to choose barbarian), that's still an extra skill point... And as for strength vs. constitution, being able to take a little more punishment isn't anything to laugh at vs. having a slightly higher chance to doing slightly more damage. So, that leaves the dwarf weapon familiarity (in a good weapon), stonecunning, stability (also good for a fighter), +2 racial saves vs. poison, +2 racial saves vs. spells and spell like effects, +1 attack vs. orcs and goblins, +4 dodge AC vs giant type +2 racial appraise/craft on stone and metal...
Now, if you turn to the barbarian, who usually wields a two-handed weapon and focuses on strength, the +2 str is somewhat better than the +2 constitution... except that the +2 constitution translates into an extra round of rage, which means +4, +6 or +8 str and con for an extra round... most fights may not go that long, but when they do, the dwarf comes out on top... Sure, in this case the movement penalty hurts a bit, but they still have a " normal " speed, and boots of springing and striding are only 5500, if you're really that concerned about the extra 10 ft... and the dwarf still gets the savings throw bonuses, and a vastly superior AC vs. giants (which I imagine are somewhat daunting for a barbarian, because they will hit often and hard, pretty much negating higher hit points and damage reduction).
So, the real problem I think isn't so much as half-orcs are so bad as to be unplayable, but that another core races is just pretty much just as good as they are at their niche. So, if the half-orc isn't even really good at what half-orcs are good at, then by extension it probably isn't going to be any good at the things that aren't its specialty, which hurts its basic desirability.
So, if I were to change it (not that I would likely be in the habit of houseruling everything when I get a chance to DM), I'd give it the aforementioned weapon familiarity (not exactly a big bonus, since I'm not sure I've ever seen a character with an orc double axe), +2 intimidate and +2 survival (which is at least as justifiable as the half-elves bonuses), make intimidate always a class skill for them and... uh... I was contemplating giving them +1 attack vs. orcs and humans, but I'm not *really* sure about that... The justification being that as outcasts, they are probably picked on mostly out of proportion by their progenitor species, thus they have to learn how to fight back at a young age...
