I actually won't call it a trade even. Because assuming if healers and tanks are good, you as a healer enabling your tank to be outside of tank stance nets more total DPS than you tunnelling more DPS. I don't have a good data to support this for comparison but MT can get as high as 1.5k from let's say 1k or less in full tank stance, while you as a healer won't get nearly as much as 500dps from enabling the tank. MT and main healer wise ofc, SCH and WAR can barely do any tanking/healing and still be fine, so this comparison is strictly the DPS output as MT and main healer.