I just casually played several no cp BG matches this week and i will try to some advice based on my experience as a solo queued player.

Stamina management is very important in no cp BG for a magblade. While you have no access to the reduce cost cp of sprinting, break free and roll dodge, Many objectives such as capturing the relic and flag requires even more running than the open world pvp. I strongly advise using the leeching strike as it give back 4000 stamina every 20 sec , very very useful. And run tri-stat food. And even you are hurrying to a relic or something, do pay attention to your stamina, dont let it fall below 5000 or you get suddenly stunned and cant break free.

Shade, as it is now fixed, works greatly for your survival. BG always have some complicated terrains and porting to the shade can save you from some really dangerous situations. And another thing i find very useful is the trap morph of fear ( sorry i just forget the name). The complicated terrains and objective-oriented battles make the trap powerful, at least for a ranged des/res magblade. Always the enemy comes to you and the objectives so throw one on the relic or flag and it lasts 60 secs. Or you can choose to put it onto some narrow roads or important points like a bridge, the start of some stairs, etc. When you have a relic on you, leave a trap on your route and it take arms and fears the incoming enemies.

This is all i can think of at the moment. Maybe i will come to add some more. Hope it helps.