Its possible to go with a tank like character. Maybe not exactly in the traditional way but its definately viable. 1h+shield with warfare skills like knockdowns, cripple, provoke, shield throw (does okish damage) and armor restores/providers from geo + whatever that armor explosion skill is called. Positioning is the key to use tank and to have that provoke ready when needed. Using a "tank" is maybe not the most efficient way to play the game but it is most definately viable in any difficulty.
Also, if you do decide to go with tank character you should probably go pure phys group to really get advantage using all that knockdown and such. If you want to still use int focused character you can do int necro with warfare and make him tankish too. The rest of the characters you can spec into dw daggers (scoundrel) and whatever you want for the last spot.
