He said HM EC, SM EC is very doable in Rakata. HM EC not so much.
HM EC is farmable in Rakata Gear; Campaign gear itemization is often screwed up; with 3/5 pieces favoring Endurance over your main stat. If you geared fully in Campaign you probably would have less throughput than full Rakata.
Most classes BiS is Black Hole Mods in Rakata Gear; and the difference is pretty minor.
Know your classes; Know the boss. My last ever raid of EC HM we took a friend of mine through who had 1-2 pieces of rakata; everything else was worse; he did 1100 dps on Mox and we cleared the place in one night with him never even being into SM to learn the bosses; This is a true story of how easy this game is