Yes, ping does have a LOT to do with it. 100 should be okay though, I usually have 60-80.

20k is not "really low". If you have 10 or less, that's really low. With 20k you can do most vet stuff except for DLC dungeons and maybe Skoria hardmode.

How do you get two 5-piece sets AND agility? That's 13 slots. How is your gear distributed? I suppose one of the two 5-pieces is only active on one bar?

With 20k DPS you can start looking into monster sets, e.g. Kra'gh or Selene. Replace the Agility then with 5xHundings, 5xSpriggan (is slightly better than Night Mother's), 2xMonster.

Make sure to have gold weapons, next step is gold weapon damage glyphs on the jewelry. Everything else should be at least purple.

What skills and rotation exactly do you use?

Rotation and rhythm is key to good skill use. I personally always do a light (or heavy) attack before a skill, in a certain rhythm. Light attack - pause 0.25 seconds - skill - pause 0.75 seconds. Something like that. The GCD is 1.1 seconds, a bit higher when you weave LA and skill, so you want to do your pair of LA+skill roughly in a 1.2-1.3 seconds rhythm.

On the frontbar you'll usually use heavy attacks as a stamina char, to regain resources. Hold the left mouse button, and as soon as the char moves the two weapons ready to strike, tap the skill key while still holding left mouse button down. Then the skill will be performed as early as possible, interrupting the HA animation at the earliest point. If you want to do another HA+skill next, keep the LMB down all the time and just hit the skill button at the right time.

EDIT: As a retro gamer having started with gaming in the 1980s on a Commodore 64, I actually use the rhythm of the spiky sticks coming out of the ground and ceiling in "Antiriad" as my weaving rhythm. https://www.youtube.com/watch?v=_irfHZ1hRYE (seek to 3:20).

Two armor pieces plus two weapon pieces are 4 pieces Night Mother, not five like you wrote.

Nah that's fine, you can keep those until you get a monster set and Spriggan. When you use Agility (which is not bad for starters!), you can only have one 5-piece and one 4-piece. So you can have the 5-piece bonus of only one set active.

Normally you want both 5-pieces, since Hunding's weapon damage and Night Mother/Spriggan's penetration are both very much worth it on a stamina char. But as I said, when you have 3 pieces Agility, you can't do that.

What's your physical penetration with your setup? Also, what platform do you play on? I'm on PC-EU (also have a char on PC-NA, but just started there, so level 5 with no CP and no gold ).

1474? Seriously? No wonder your DPS is too low. Where did you look that up, please double-check if that's correct. Maybe take a screenshot.

General rule is: You want to reach 18.2k penetration cumulative from all sources, i.e. debuffs on the target, buffs to yourself, and your gear penetration value. Target resistance is deducted from your damage done after all other calculations are made, so getting close to penetration cap is the most important way to increase damage done.

You usually have a tank (or a skill of your own) to apply Major Fracture to the target, which reduces resistance by 5.2k. If you have a tank, they use the Crusher enchant and other skills that further reduce the resistance. Templar healer can apply Minor Fracture. I usually go for 11-12k penetration since I mostly don't play in highly optimized raid groups where you need much less.

So try to get to 11k with gear and champion points. Spriggan is a very good start, Kra'gh one-piece also helps.

Also contact me in-game if you like, @Loc2262.

Yes, that addon shows it properly and I use it too. So yeah, my previous suggestion applies, you need much much more penetration.

Get the Lover mundus stone and have as many Divines armor pieces as possible.

I do use Sub. Assault twice when I'm on my front bar.
I have Warrior mundus and all my armor is Divines.

I've put 49 points into Piercing, and gonna try Lower!