Stamina Warden PVP / PVE Gear
PVP != PVE.
The sets you have chosen are primarily PVE (except briarheart, which is usually more for PVP).
For PVE have a look at this:
Btw. crafted DLC sets like orders wrath (one of the best non trial set and easy to obtain) can be obtained even without owning the DLC. Buy it (guild traders), lets somone craft it (friend / guild mate / random) or find someone who hast the crafting tables of this set in his home (almost any bigger guild has a guild hall with all crafting tables) and craft it yourself.
For finding guild traders that might sell it, have a look at this:
For PVP you had to redo your whole build and the reason why you do good might be because you are matched with lower ranked players or had the luck to get good teammates and bad enemies. The bad thing is,
I dont have an up to date guide, might give you some older ones, from patches ago. Also it depends on how / which role you want to play in PVP and which type of PVP you want to play (cyrodil, imperical city, duels, battlegrounds, which mode). An optimal build might look completely different. Also one build might work in one encounter but fail in another, depending on your enemy, because PVP builds are somehow individual (besides some strong meta builds).
Maybe a combination like vicious serpent + orders wrath or leviathan + orders wrath, medusa + orders wrath or berserking warrior + orders wrath would be an noticeable improvement. All of them avaialable without owning any DLC.
Medusa can be obtained in the dungeon Arx Corinium (you should only wear it on weapons and jewelry because it is heavy). It is stronger than the other options if you dont play barbed trap and weaker if you already gain that minor force buff from barbed trap or another source. In my opinion you should play babred trap because it is a really strong skill so this set will be the worst option of all of them but you wont need to care about the barbed trap buff what might make it easier for the beginning.
Leviathan can be obtained by doing Crypt of Hearts 1 & 2. Its better than medusa if you play barbed trap, worse if you dont.
Vicious Serpent can be obtained by doing Hel Ra Citadel, Aetherian Archive or Sanctum Ophidia. All of them are trials, but they are the easiest 3 trials in the game (especially the first 2) and all of them are included in the base game. The set can drop in normal and in veteran but in veteran you have 5x the chance that it drops. Also curated loot works a bit different for those 3 trials. It is as strong as leviathan but will give you on top of the damage also big sustain, you probablly wont run out of stamina anymore with this set.
Another option is berserking warrior, which drops only in Hel Ra Citadel (easiest trial in the game) but the chance for a drop is 5x higher on normal than on vet (also curated loot works a bit different in here). Its stronger than leviathan and vicious serpent but works only for melee characters.
Orders Wrath, strongest of all of them because the buff is unique and stacks with barbed trap (not so for medusa). But only if you dont go over crit (which you wont do if you arent in optimized trial groups). Just buy it, let someone craft it or craft it yourself, easiest / fastest to get in my opinion.
Especially if you combine Orders Wrath with Berserking Warrior you have 2 A-Tier sets and there are only very few sets left that are a little bit stronger.
Are you using the full Slimecraw Mosnterset? If so, thats bad, because the buff is usually already provided by healers (combat prayer) or can even obtained by yourself by using the camouflaged hunter or even the warden skill bird of prey. This way you waste the whole bonus. Slimecraw is usually only used as 1 piece if you cant get a full monsterset because you are wearing a mythic for example.
I suggest to switch to another monsterset. Just take stormfits its one of the easiest and strongest monstersets. Its so strong that it is even often the best option for Magicka even giving out a Stamina bonus. Also its just equip and forget, you dont have to consider anything special and your DPS just automatically increases.
It can be obtained in the dungeon tempest island (only on vet).
There are also some other options for monsterset but they are often weaker, situational or more difficult to play, sometimes even all of them at once (except Maw for Sorcs).