Hi. I'm a Vanguard tank.
I completed Lost Island HM, but was only able to do so with RDPS. When I went with melee DPS, we consistently hit the enrage timer. It was not a failing on my end, or the healer's end (which should be clear since we hit the enrage so much.) I interrupted incinerate every time, usually even before it got to 1 stack, and I was always above 50% health (so it wasn't the healer's fault, either.) It wasn't the DPS' fault. They never died, and they had Rakata gear. We had both the DPS switch to their ranged alts (who had about the same gear) and beat the boss on our first attempt.
Lost Island is poorly balanced. You can pretend that it's not, but it is. You can say that you're better than everyone because your group did it with MDPS, but it's probably because you're just better than everyone. Congratulations, you have won an MMORPG. Go get a tan, or treat yourself to a cake. That does not mean the fight is properly balanced, it just means you were able to succeed in the face of adversity. Once again, congratulations, your majesty, king or queen of MMOs, and conqueror of lady or man parts. Maybe being great has gone to your head and made you stupid. Or maybe you just don't don't understand the concept of balance. Whatever the case, if you think Lost Island HM is balanced, you are wrong. Lost Island is a GREAT instance. It is tons of fun, but it also needs tons of work. Open your eyes.