On the subject of missions and strategy.
As far as I’m concerned this is the order of levels in terms of overall difficulty.
The Sentinel
The Voids Edge
The Renegade
The Algorithm
The Archive
The Experiment
The Heliophage
The Saboteur
The last three I consider to be about the same difficulty depending on team size and composition.
Overall strategy:
For the love of all that is good stick together. I’ve seen level 100’s just run off and die while cursing the rest of the team for not being good. The team that stays together lives together. Make sure you prioritize distance by your support. Miko is fast but you cannot be its only concern.
Tanks hold the line with your melee companions. Even as Montana you really need to be up there or your melee units will die. Tis better for you to be taking damage than Rath until he’s like level 7 then you can just let him do whatever.
When defending any structure or unit please have at least one person on the point or you will likely lose. Thralls can and will sneak up on it. Also make sure any ranged units are taken down first as they will be doing most of the damage to that structure. Most importantly know where the enemy will spawn. On the Saboteur this is critical.
I still just prefer Reyna and Alani as healers on most advanced missions because of the increased offensive potential via scoring critical hits more easily and the fact their healing comes in bursts as opposed to ticks. Miko has very strong tick-healing, and its crit damage is very nice, so I feel it is a good choice too.