Im always torn between heals or rage for mass drags. Sometimes heals help the drag withstand a little bit longer, which can be a difference maker. But sometimes rage is a must to quickly break through that town hall and cc in the middle.
I think its very situational, at best perhaps.
There are occasions where Heal would work, however at lvl 6 40 HPS vs lvl 6 230 DPS mathematically you are much better off with a well placed Dragon with a rage in its path to the AD.