I forgot to add one more advice to my post above... *** Do use tactic boosters when you can against 3 chevron mobs. Sometimes, they get some high rolls and can beat your arse down, sometimes they get crappy rolls. But when they get the luc...
There is a lvl 16 green shirt that gives +10 to Handgun Tactics and +10 to Retaliate Tactics (Retaliate is the green button). This shirt is awesome in Interlock since Duelist is interlock based. For ranged, you will need to get the lvl 20...
Depending on what your class is, best mission for max xp is placing timer on "tiny" and difficulty on "hard". In addition, you will need to get those 3 part missions to get full xps. If you are only getting 2 parters (that are not critical...