In Path of Exile, if you made LL RF mana guardian with watchers eye, having enough poe orbs, and 6l shavs, shapers touch, doon, and prism guardian while stacking str and mana. I will say that the defensive side is good, im lvl 75 with almost 12K es and 50K armor (90% phys mit). However the single target with Scorching ray just feels so terrible even with a 6l. Your damage feels bad on LL RF Mana Guardian. What would you do?
In fact, your boss dps will never be ‘great’ but it does get decent enough once you pick up more ES/Mana nodes from the tree. Getting an opal with es/mana/fire damage will help, same with a unsocketed ring. Eventually you might want to replace the doon with a good rare scepter, play around in POB with possible rolls, but ideally you would want a good fire roll/burning/spot for damage over time leo craft.
You need to swap increased AOE with Conc effect for bosses. Unless you plan on mainly using SR to kill bosses you probably want to put RF in your 6 link using arcane surge and swift affliction. Since you are using shapers touch and memory vault you can’t use essence crafted gloves/hat to make a 5l for RF.
What you should to do is that:
1. At the moment you have absolutely no stun mitigation, which is very dangerous. There are 3 options to fix this: Presence of Chayula ammy (probably not for you because you go Astramentis), do uber lab and get Bastion of Hope ascendancy or go south and grab Unwavering Stance. Use the Brine King pantheon as a stop gap.
2. You didn’t take Pain Attunement. This node is extremely important especially because you focus on SR. It’s better to sacrifice Arcane Vision and take PA. Just run outdoor maps and you’ll be fine.
3. Because mana guardian has a lot of ES (a lot more than classic LL RF SR), it’s better to put Righteous Fire on your chest to 6L it. Do it with: RF – EF – BD – Conc – Arcane Surge – Swift Affliction. Put SR on 4 link poe items.
4. Corrupt your Purity of Fire to get level 21. If you fail, either level up a batch of 6 on your swap weapon slots, or buy one (around 95c). This will increase your ES regen.