To take maybe a slightly different tack on the OP's question:

Solo duties where there are clearly many, many other people around you utterly fail to take advantage of the trinity. If I'm running the MSQ as a healer, maybe the solo duties should focus on my ability to heal everyone else. If I'm running the MSQ as a tank, maybe the solo duties should put me at the vanguard, drawing the attention of the enemy and keeping them occupied. If I'm running the MSQ as a DPS, maybe the solo duties should really test my ability to squash the enemy before they overrun everyone else.