Unfortunately, hp fire is an uncommon thing:hard to get right
Shiftry is never seen in ou tier. More like ru tier.
Try chansy/blissley vs shiftry sp, and watch it fall. Shuckle counters with sandstorm,toxic and swagger.
What about skarmory and mantine. Skarmory walls shiftry, bar hp fire :-( mantine is a special wall, countering with rain dance, ice beam or a flyingtype move