Hey there
this is what I mean as I record a quick video a while back -
It works well because the cooldowns are not shared so when you switch between Bear/Spriggan you arent hampered. I use the Quiet Forest belt for Spriggan mana regen
I didnt really showcase the Werebear switching as I rarely use it, but look at the end I quickly shift against the Mono boss which is not required only timeline bosses
edit: I remember now in this video I was stacking timelines for XP testing and I think I ended up closing the monolith at around 51 timelines done, Spriggan rarely was troubled I was more at risk of death than the companion but you can even use Root Wall for decoy and you have Healing Totems on summon/on hit which heal for a tonne