Luck of heroes, if it is left a luck bonus, is not balanced with the other +2 to one save feats. This is because in 3e, most every bonus you get is done as bonus squared (for magic items, for example) to determine how good it is and all that. The stacking rules enforce this. So luck of heroes, as it is written, provides +3 to saves total, but if you go by the squaring rule then the other feats add +2 (squared)=+4. I would say, however, that +1 to 3 saves is perfectly balanced with +2 to one save, but ONLY if luck of heroes isn't considered a luck bonus.
I should mention that I really dislike the way that stacking is handled in 3e, for the most part...some things obviously shouldn't stack, but saying that a halfling gets less of a bonus from having a luckstone than a human does doesn't make much sense to me.