So UMA is useless without H@H right??

No, it's not useless. H@H plan just gives you unlimited minutes over UMA. Without H@H you can still use it but your minutes are deducted just as if you were using EDGE.

I use UMA all the time and I don't have any extra H@H plan.

I am roaming internationally right now and using UMA i dont have to pay those ridiculous fees when making or receiving a call.