Generally speaking HR is better even if its just hitting 2 Players. There are obv exceptions. Usually the tank shouldn't eat so much damage, that you need to DL the Tank a lot, if he does he should use CDs. Especially hardcasting DL usually doesnt work.
HR on the other hand does a few things. First it generates HP (does DL on Beacon also). Second you might by accident hit players with it and heal them. Third you refresh IH on them. Beacon Heal should generally be enough outside of Tank burn phases which there are not so many this content.