Cloister 93%IV (FrostBreath/Blizzard)

I have a 100% Cloyster. While it's not bad against Dragonites as long as you dodge everything, its low HP just leaves it to die if you don't. Great DPS though, so it depends on your dodging skills.

Cloyster is excellent Dragonite cutter as long as you dodge all quick attacks next to charge attacks. Basically the same like Victreebel.
I always dodge everything so I am completely satisfied with Cloyster's low hp and manage to easily take down 2, sometimes more dragonites in a single run (depending on Dragonites movesets).

Before I got a second Lapras I had better success with electrics against Dragonites than I did with a Cloyster. A Dewgong worked well too.

i use a 84 % cloyster with the same moveset, 1700 cp, reks up to lvl 2500 dragonites, if u evade only there chargeattacks, it only handles 1, sometimes 2 if ur lucky, but its really fast in taking them down, u need 1 blizzard and 2 more autoattacks

I have a nearly the same Cloyster as yours except its IV~98%, but I prefer Slowbros with Ice Beam to take down Dragonites here as it's hard for a CP~1200 Cloyster to cope with those CP3000 Dragonites.