Since you're asking, the Balance and Ahk Morning have already assessed the difference. Both Direct Hit and Determination are a 0.1% DPS and DPS/Healing gain, respectively. It takes slightly less Direct Hit to gain a full percentage; 24 points in Shadowbringers compared to 25.3% needed for determination. For the sake of argument, I'll use last expansion since we have that
exact data At 720 melded Direct Hit, you gained 3% DPS while you gained 2.85% from Determination. Let's round that up to 3%, and since you mentioned Sage, I'll use Ixochole. If your Ixo healed for 5,000 with zero melds, 3% would make it heal for 5,150. You gained paltry 150 in the best case scenario. That's roughly 0.16% of a Dark Knight's HP at full i600.
Put simply, your Determination melds accomplished nothing. They contributed nothing and in no way helped heal Living Dead once you factor in even using your entire kit would only net you less than 1,000 additional healing. Frankly speaking, the difference between Direct Hit and Determination is negligible. Direct Hit only has a very slightly benefit because Healers don't have any naturally but the gains are small enough you'll hardly notice outside of serious min/maxing. The same logic applies to Determination.
Next time, do your own research before demanding other people provide proof to a system you're arguing against that has been common knowledge for over two years now.