Crit star absorbtion

You could avoid teaming them with archers and riders. On average they have the highest crit star weight. Other than what you already put up u'll just have to build a team around them that can generate stars but have low star weight to not soak them up. Mystic code's anniversary blonde can give you tons of stars if its lvled and royal brand can increase the Zerker or Avenger's absorb rate too.

Classes will have weaknesses that you can never totally mitigate and you just have to deal with some bad RNG.

Either generate 35-50 stars or use CEs that got + star absorption rate but it is not recommended. The only Avenger and Berserker I know with star absorption are Jalter and Raikou

We can do some ways for Berserker and Avengers critical damage rather than CEs, except some Berserkers and Avengers indeed have own star adsorption skills (Raikou, Lancelot and Jalter)

(1) yeah, generate enough stars. Well, in the future Dantes+dual Skadi is in fact this way since you dont really need to consider if Dnate can absorb star or not, you will have >40 stars though Dantes' NP spam each round even without 2030s.

However recently it is not quite accessible. Then Jack in most cases is required, or dual 2030 Merlin if they can spam their NP.

Servants like Atalante, Drake, etc is another option, particularly for one turn bursting of brave chains of your Berserker. Anniversary blond as Mystic code, or using combo of combat suit mystic code + Golden Carp Figure CE to switch submember bringing stars for your Berserker/avenger for 1-turn critical punch.

Caster Gilgamesh is also a good supportive option. He dont have such high star weight, but his 1st skill and NP can provide tons of star. However, (1) it depend on your Berserker and Avenger's own hit accounts, and (2) He is more compatible with Art team, but not so many Berserkser/Avenger are Art-based.

(2) Roll for Brynhild. Her 3rd skill after strengthening could be excellent for any berserkers if you want these Berserker as critical DPS. But off course you still need 2030s or Jack to generate star. Also right now her 3rd skill is still not great enough for Berserkers and Avengers.

(3) Sealing Designation / Enforcer MLB is the best for star absortion, but still not enough especially for Berserkers (only enhanced to Lancer's level). But you can combine the (1)(2) tactics, like with 2030 Merlin/Hans-Jack, with additional Berserker (such as 2030 Nightingale/Dantes) to reduce team star weight then enhance your main berserker DPS's star weight.This idea is quite common for some dual Berserkers team like dual Cu Alter+Waver/Merlin, Cu Alter-Waver/Merlin-Nightingale, etc. Generally 2030 is really important.

Would also like to add to other posts as I didn't see it mentioned; the recently re-released (rare prism exchange) mystic code royal brand from fate zero event has a skill that grants +1000% crit absorption on the target for a turn regardless of skill level. I've been using it for my avengers and it works great, though you can probably only use it once a battle as with most mystic code skills.