In terms of tactics, try to keep your distance. You can avoid flamer-bearing infantry easily enough if you need to.
If it's bikes with flamers or something of the like, good: they're paying extra points for the toughess there, and splinter weapons will thank for it.
MSU assault is a weird but viable answer too - each unit can only fire overwatch once per phase, and DE can really keep the minimum-sized Reaver squads coming.