was considering trying out duel, but...

In most cases against a single opponent, you would avoid items that provide dual protections, since you're mostly only going to take damage from one source. It's very, very easy when the enemy is physical, since minions, towers etc. all do physical damage.

It's a bit different perhaps when facing a magical enemy, since if you're fighting among the minions, or diving under their tower, you could take both types.

But for the most part, I'd say it would be very situational. So where I see one of your builds has Berserker's and Bulwark, you just wouldn't do that. If you're facing physical, Berserker's is fine but instead of Bulwark, get Contagion or Midgardian or Blackthorn or whatever that's not so focused on magical.

You have to start eventually. Arena is fine and all, but you're not getting the full smite experience if that's all you play. If you're afraid of getting BMed by your team for playing bad, then play with friends.

That is what i was thinking but i was thinking about the minions and also the bull demon and the buff camps and i was also considering the passives as well.

Never build prots that isn't the type of damage your duel opponent has, there are very few exceptions I can think of, like Magi's cloak (and thats not built as the primary defense item) but 99% of the time that is the general rule.

Ymir: Either start with Hunter's Blessing, Tiny Trinket, and 2x Healing Potions and Mana Potions OR Talon Trinket and 1x each potion type. Build Shoes of Focus, Bancroft's Talon, either Breastplate of Valor against physical or Genji's Guard against magical (build Pestilence against Hel, Aphrodite, and Anubis), Demonic Grip, Telkhines Ring, Toxic Blade if needed for anti-heal, and Polynomicon. If your opponent builds crit, replace bov/genji's with Spectral Armor.

Levelling order is: 2x Glacial Strike and 1x Frost Breath at the beginning, then 1x ice wall] at level 4, and 1x [[shards of ice at level 5. Prioritize gs, then fb, then iw. Put points into soi when you can. Use gs for wave and camp clear, and fb for poke, CC. When you're attacking objectives once you have poly online, strike the wave/camp, then use basics until either Poly's reset or your opponent is attacking you. Proper use of Poly combined with the AS from demonic can pump out some crazy damage. Go watch how Hatmaster plays Ymir for some real pointers; he almost exclusively plays guardians, so he's a good source for Ymir. By the way, do NOT play Terra in duel; her cooldowns are way to long and her abilities are to easy to juke. Save your hair and try someone else like Vulcan or Bellona. Good players will generally ban Skadi, Ullr, He Bo, and AMC. Chaac is okay in duel provided you can get an early lead, but he tends to fall off late, so you have to be careful with him. Also keep an eye out for opponents who will backdoor you by ignoring you and going straight for your phoenix and/or Titan. So by wards and keep them up as much as possible.

duel is its own cup of tea. every match is different and it can go from a fighting opponent to a backdooring one (as the maps allows it)

Just a general note about your concept builds. I think you're quite stuck in a regular team mindset, while duel is a lot if not all about counterbuilding. The reason for saying this is just looking at the number of prot items you have.

What I have noticed from youtube is that in most cases you will see a damage item start into boots into defense into other counter items (anti heal most often and pen). With your build an opponent will just get a big % pen item. Then you lack the damage to kill him as he countered a big part of your build.