Even though Dragonite is an 'Uber' pokemon, his weakness to ice (type / lowish special defence) make him an easy target. Also, his Atk is by far his stronger aspect, so you have to rely on the Physical branch...most of the best moves are Special :L So usually when EV trainin I'd train Atk to make the best of it. I feel cheated if I raise Sp Atk :L
Although Earthquake is pretty awesome.
Personally I rank him as only moderate. Good/charismatic enough to make the team but not enough to go pro with <object class="emojione" data="
https://resources.enjin.com/1489581540/themes/core/images/emojione/svg/1f642.svg?0" type="image/svg+xml" standby=":)">:)</object> I'd usually team him up with a Gengar for the speed/Earthquake in double teams.
Blaziken is a suprisingly good Pokémon for Competitions, although most people lean on Ubers (Garchomp etc) and Legends (Rayquaza) where possible, or the hilarious Rattata that can KO any unprepared trainer. XD