Is the Leech from Physical mechanic meant to effect later DoT calculations like poison?

So I'm swapping between two fire res rings. Pretty similar, but one has 5% leech on physical damage going to Mana. But equipping it I notice my poison damage DoT going down. I had expected it to go up as this ring also had a small but bigger boost to Physical Damage. 6-12 instead of 3-6 or something like that.

So it looks like that 5% is being removed, and then the damage my poison is based on is reduced.
Working as intended? As in way it makes sense as written, but trying to look it up some say it isn't meant to make a difference.
Thanks

Edit: NM, found it was due to a +Max HP mod on the ring. Working with a damage bonus if I'm max HP, it screws the numbers up. As the game updates your max HP when you equip the ring, but doesn't give you the HP until the game runs, it kills the 'bonus at max HP' that's in the damage calculation already.
Have to leave the ring in, let game run and give you HP, go back in to see the new damage numbers.