I've yet to actually use my Dragon Strike minis for HeroQuest, so I have no knowledge of the best stats to use with them. The only ones I've seen were done by Dewayne Agin. You can find them in the
Agin's Inn Archive. Under the 'New Monsters' link at the bottom of the page he has two Dragon Strike miniatures done up with stats and rules. Take them as is, or mend them to your needs.
Thus far I've only taken miniatures from HeroQuest and made them special characters in some of my quests, mainly since I've only acquired Dragon Strike in the last year myself. Same with Dark World. Would love to have Warhammer Quest. I'd like some of those spiders and bats in my collection...
A good rule of thumb is to take a monster and judge for yourself if they are stronger or weaker than say, a Fimir. Then adjust the stats of the Fimir to make it stronger, weaker, smarter, etc. depending on where you believe the monster should fit. That's the best way I've found to keep things simple in the spirit of HeroQuest and to ensure you're not creating something that is over-powered or far too weak.
Hope that helps. As always, everyone else is free to chime in with their thoughts and ideas.