Q: Why hasn't there been a [insert type combo here] Pokemon?
A: Because GameFreak wants you to keep buying the games. Do you really want them to run out of new stuff quickly? By Gen 4 or 5 we'd have all type combos represented if they released them at the rate that the fans want, but then after that there's nothing new to do in terms of types.
Since they haven't, we can still get hopeful for unused type combos. If they were all here...we wouldn't that hopeful feeling, at least not for that particular detail.
So, in a way, GF is giving you the gift of anticipation.
I'm not against religion. I'm against all bad ideas, held for bad reasons, prompting bad behavior.
Ice is the worst type by far look what it did to Kyurem... UBER candidate sent to BL on the basis of being Ice dragon...
Defensively Ice resists nothing and has many many weaknesses to key offensive types like fighting rock and fire and also has a weakness to steel
Offensively Ice may be good but it is not the best in the game (that would go to fighting which also gets a key rock resist)
Poison and Grass might not be the best but they are nowhere near Ice tier bad...
so far Yanmega is the biggest missed opportunity for a dragon/bug Pokemon.
However we could use another line from the dragonfly family maybe one that incorporates the full life cycle After all their larva are some of the top freshwater predators dining on a nice diet of both bugs invertebrates and fish)
Larval nymph(Water/Bug)(300-400BST)(swift swim/?(hidden))->fully grown nymph(water/bug)(BST500+)(swift swim/?(hidden))->Adult(Dragon/Bug)same(500+BST)stats reallocated to be faster and more offensive(levitate/(speedboost?(hidden )
We could even make it a Damsel fly to avoid repeats after all they kinda look Draconic with their back swept wings...