Full Justiciar set is the beefiest armour you could obtain.
If you do not have money for it however, I personally just use guthans to heal myself up on minions whilst im doing bandos and dinhs when i want to focus less.
I usually just bring two alts and put prayer gear on both of them. I use the alts to tank the minions that attack with the style I'm not praying against on main.
For example, at Bandos, I'm already praying against melee. So, I would tank the melee minion on my main while killing the boss, and tank the ranged and mage minion on each of my alts.