What do you currently have him at Critical rate wise? Does swapping the gauntlets out for either the DEF or the HP gauntlets that you are describing affect the Crit. Rate stat at all?

Apoc is able to basically do a full heal on an ally assuming you have the crit rate for it to proc.

Both HP and DEF are important, while intrinsically becoming pointless if either one were to be without the other. Generally, a good happy median here for an even ratio is 1000 DEF for every 15000 HP. After a certain amount of DEF, however, I believe its around 4400, you start to see diminishing returns on the effectiveness of your champion' mitigation. There is no limit or bottleneck for HP though, and I always shoot for this first before DEF, except in cases of having DEF DPS champions.

You can have a crap ton of defense and no hp, you will get killed everytime before you can take a turn. You can have a crap ton of HP and no defense, and very well survive as long as your attacker's damage after calculation doesnt equal anything higher than your total HP stat.

CR% is nice, but by far the most important stat for Apo is SPD. You need him to be as fast as possible so that he can continue healing and TM boosting your team.

To your specific question, DEF is typically a better stat up to around 3200, after which HP tends to be better. That said, I'd caution you about spending silver on 4* items. Judging by the rest of your stats, you should be past the point where 4* is worth investing in. You may even be past the point where 5* is worth it.

A 6* rare item is better than a 5* epic item, and is often better than a 5* legendary item. This isn't always the case, but for the 5* item to be better it really needs to be rolled perfectly. Couple this with the lower number of points returned on artifact enhancement for 5* items compared to 6* ones, and it's pretty much a good rule to follow that if you are able to farm 6* items, you should stop upgrading 5* ones.

Your stats on Apo seem good enough that you should be able to farm Dragon 20. If you aren't, then I'd suggest posting your roster so we can help you build a team that can.

Id say at 247 speed, he has speed boots equipped and most likely a few rolls of speed on the gauntlets also 🤣

And you're going to make this poor guy delete all his 5 star artifacts kram, hush. Lol.

Speed, def, hp and res.

I strongly disagree on ignoring 5star artifacts at your level.  Especially 5star legendary with 4 good substats.  This is what I consider a guaranteed quad roll  :) much better than rolling a rare 6star  and getting flat stats at 12 and 16 at twice the silver cost.  And at 150 days in 4star gear will certainly still be used.

I agree with kram that CR should not be priority, if you need the full heal the other champ is gonna die more often than not anyways lol.