Honestly I think for most crossfire worked best with the older drivers you were using. Unless you need the newer drivers for something not working, you don't need to change. They have made a ton of changes that affect the 18xxx drivers and crossfire stability is probably at the end of the line for getting fixed. I am a user like you and this is just my opinion. I don't know anything for a fact with AMD.
If you want to try another 18 series driver I would suggest the 18.3.3 or 18.3.4 they seem to play nicer with the R2 & 3 series of cards. If you want the best older 17 series 17.7.1 seems to be the last one most everyone agrees was good.
On those 18 series drives you will want to slide the "power limit" slider to the right to its maximum. This helps the stability on those drivers.
Hope that helps.