Hmmm. The chance for disappointment is high. However I have found that a B/SE Tyranitar really is a monster situational attacker in the current meta. For my most important offensive needs he is a good source of decent speed and tankiness to take out multiple Blisseys (especially if they do not have DG) and Snorlaxes. I know you already have a DT/O Dragon which your B/SE performs similarly to in sims. Are you getting stonewalled in your Blissey takedown attempts with your current roster?
I don't need to tell you of the rate of return per candy on powering up the level 30.5 mon. You already know it is crazy high and will not impact performance in a huge way.