So i just saw moxsys update on his chain zane build.
I was allready running an ib/vr artifact before and my barrier would go down quite frequently with 2 points in GM.
He pointed out that GM had diminishing returns, as the skill states, but i never thought much of it. So he only put one point into it, which makes perfect sense.
This freed up one skillpoint for me and then it clicked.
Put it in borrowed time, since it increases max duration and GM restores % of max duration.
After some testing i ended up with 3 points in bt and my barrier would never go down during the takedown, even in between fights and running to the end of the bridge.
Still figuring out the sweetspot tho.
3 points seem exzessive, but 2 points might not be enough.
So if you too have trouble maintaining barrier uptime, i highly suggest experimenting with bt.
Sorry if this is old news but i never see anyone investing in bt, so i just wanted to let you know