Honestly, you're better off with Focus Blast rather than wasting the moveslot and item slot. Sure you may miss, but if it hits you're gonna be doing this:
252SpAtk lvl 50 Hydreigon (+SAtk) Focus Blast vs 252HP/4SpDef lvl 50 Tyranitar (Neutral): 141% - 166% (292 - 344 HP). Guaranteed OHKO.
1st Place Winter VGCS and 2nd Place Long Beach Winter Regionals!