There's nothing bad per se about the idea. There are even times where it might make sense (when shields can nullify a mechanic you don't want to, like in O2S).
It however is usually suboptimal. Any damage output that can be healed with HoTs usually only requires one set of hots. Having two of them will overheal a fair amount. Also, scenarios where you get two sets of incoming damage play out a little differently. In one case you could heal the first set with shields and then heal the second one with another heal. In the other case (without shields) you might need to heal the second set twice because of the lack of mitigation.

All in all it's not that bad unless you're really trying to squeeze out some optimisation.