im trying to figure out what materia my tank would need in currently using the i250 crafted set
http://ffxiv.ariyala.com/WXKN
and wanted help figuring what skills to focus on

You need about 710 accuracy if you don't want any misses on A12S. That number may not be accurate but I know that will ensure you won't miss. However, if you don't plan on doing Savage content then you don't need to meld accuracy.

As for your melds, You want to meld Accuracy to cap > Crit V > Det V > SkS V > Crit IV > SkS IV > Det IV. And for accessories you'll put a STR V into the first slot.

Here, I took your link and did the appropriate melds, with G5 materia along with a G3 on the belt to fully cap Crit.
http://ffxiv.ariyala.com/WXLU
If you can't afford the large amount of G5 Materia, then G4 will do. Just make sure to change the melds and watch the stat caps accordingly.

Also, could you explain what you mean by what skills to focus on?

sorry by skills i meant accuracy grit set skill speed, i just looked it over so i dont need to meld the helmet then i saw you left that one blank or should i det since crit hit cap?

Oops. Sorry I forgot to do the helmet. Not a good idea to do melding at 2 in the morning. But for the helmet you'd put all crit materia into it.

thank you ill start working on getting and melding the materia