“Put those Charged TMs away, Trainers!"
"As you are going to need them to Fire Blast -> Crunch -> Fire Blast -> Crunch -> Fire Blast -> Stone Edge your freshly evolved Smack Down Tyranitar!"
Answers
Yes, it's damage is low. But it is both the best Rock move on good pokemon, and it hits really fast, which might be very important if PvP ever becomes a thing, almost impossible to dodge without guessing. Would you rather do 100 from Stone Edge, or 45 from a dodged Solar Beam? (Yes, that's apples and oranges because Rock vs. Grass. The point is about how being hard to dodge is a good thing maybe.)
Gone up against Stone Edge in a gym? Not fun, you'll get that stone spike thing up your hindquarters almost every time, it's quite difficult to dodge, and could be impossible if a real player were controlling the opponent.
This is why I've been thinking that Smackdown is getting a little overhyped. For the hardcore players with plenty of CTM's to spare, sure, it will be fine. I feel like there are going to be a lot of disappointed players who end community day with only 1 or 2 (or maybe even 0 for those on the bad side of RNG) double rock Tyranitars.
Any Tyranitar caught or evolved from a Pupitar in those three hours is guaranteed to learn Smack Down as a fast move, but there is only a 1 in 3 chance that it will immediately get Stone Edge as a charged move. If it gets Fire Blast or Crunch, there is no way to know how many Charged TMs will be spent getting Stone Edge.
I for one aren't swimming in charge tm's, my bite/s edge variant is a great mon to use, is maxed, and I will carry on using it when CD has been & gone. My army of double rock golems have served me well in raids against the birds, and won't suddenly become useless when SD Tyra becomes a thing next week. That & I'm working next Saturday so no sour grapes whatsoever!!
No, all those rock mons won't become obsolete, but they'll be an entire tier lower when it comes to the best rock mon. And you can cite stats til the cows come home, but at the level 39+ club most of them want is the best. And that's now going to be the Rock/Rock Ttar.
I have noticed a slight uptick in CTMs in recent raids. I currently have 7 CTMs, which is 6 more than I had a week ago. I suspect I'll get a few more with more raids.
In any case, I've never seen any one Mon so dominant that it renders others useless. Some are better than others, but a maxed out rock/rock golem is never going to be a bad thing, even if it is going to play second fiddle to the rock/rock ttar.
This is the first community day mon where the possible moveset is cooler than the possible shiny. Dragonite's was nice, but Outrage is still killer. But giving a rock fast move to Ttar? That "rocks." I know it's lame, but c'mon...it's just sitting there!
