best RAID progression tank

[flzk]

hello, we are a semi-hardcore progression guild 3days/4h per week and going to dipp into mythic progress this weekend.
currently our tanks have all classes on a 850-860 ilvl so we can choose the "best"
what class combo would be the best in your eyes for a pure progression purpose ?

[Dangg]

The current top progression guild seem to use Warriors and Druids.