That said, I've had a couple of games against Orks with very few vehicles and actually been quite grateful for the long ranged AP
When you have to deal with horde armies they're very handy.
They are excellent at reducing infantry at range - something the Tau Railheads don't always do well (5+ to hit inf less if you have to move fast) and their infantry have too short a range of AP. They are excellent to add to a Mech Infantry formation when they're tasked with dealing with enemy infantry/tanks.
Not sure I'd say reducing infantry at range, they're far too expensive a platform to use to actually kill infantry - however they're exceptionally good at adding another BM or two to any formation across a wide area. Lets you play that little bit riskier because you know that if your main formation falls just short of breaking a formation, the hammerheads can just nudge them over the line.
Again, with orks, it's particularly useful as they're able to shed BM like nobody's business so up close it's often a case of all or nothing - if the unit's not broken they can take you out in assault.