I only know of some groups that use Tank LB on Turn 4. But in all honesty, the better geared your group becomes, the faster things die, so Tank LB is not really neccesarry. We reached the point in Turn 4 where nothing is alive at the same time with a DN except for the stuff that pops with him...so we just use a Meele LB on the last Dreadnought when everything else is dead and take of around 30ish % of his HP in one LB.

Some people like to use the LB on the Adds...but I think it's a waste.