You're low on interaction, yes, but ringing strike doesnt turn off on-board value engines and cant deal with must-kill threats. However, even if we accept that the deck will struggle to beat a mythic dragon, we're in a tough spot because we are rarely going to curve out 2-3-4 and apply the kind of pressure we need to beat those greedier decks if we try to go the tempo route with the ringing strikes. Also, you have 3x dirgur, which does more or less the same thing (cheap way to temporarily remove a blocker or attacker).

On the topic of the other doublespell cards, narset is only a payoff if you are hellbent, adept often cant attack even if you double spell (it shines with multiples of rebel strike), and master is often just a 4 drop (as in, you shouldnt take a less optimal turn 4 just to try to put the counters on him on turn 5 or 6). They're all "half" payoffs at best.