I've just finished the Return to Hoth campaign, where I was playing Mak. The other heroes were Jyn (often our utility person, with high speed and free out-of-turn movement), MHD (entirely focused on healing), and Biv (tank build). MHD was probably our MVP for the entire campaign, but in the final missions Mak and Jyn were the ones who were really carrying the ball. I think Biv was only wounded once in the entire campaign (thanks to his droid friend).
I play a lot of skirmish, as does my son, who was part of our group (playing Jyn), so our combat tactics were pretty good, even though our campaign tactics were sometimes lacking. However, the Imperial player was also excellent; we play at our LGS as one of 3 campaign groups, and he's known as the most skilled and challenging Imperial player of them all.
For the first half of the campaign Mak was virtually garbage because he was stuck using his utterly crappy BB rifle. But as Rey says, "The garbage will do," and eventually that was right. lol We were 1-4 for our first missions because we quite simply didn't have the damage output that we needed; it was often taking us 2 or 3 attacks to kill a single figure, while the Imperial player was able to keep putting out more and more figures each round. It was actually quite discouraging at first. All of our money was being spent on Biv and Jyn as our main attackers, and we also weren't drawing enough rifles for purchase. About mid-way through the campaign we picked up enough weapons that Mak could start using the E-11 as a hand-me-down from Biv. Finally, things got absolutely SICK when we happened to draw and purchase the DXR-6 risruptor rifle with 3 or 4 missions left; we were undefeated after that, and only 1 of those missions was really very close.
These were the upgrades I purchased for Mak, in order:
2 xp: Jeswandi Training (+2 Health, and become Focused when an enemy within 3 attacks)....This upgrade is GOLD. The Focus was really the only way I could do significant damage for the first part of the campaign, until I gained the E-11.
4 xp: No Escape (2 Strain: exhaust to become Focused and attack again)....Insane, especially after he got the DXR-6 (RRG for attack dice!).
3 xp: Execute (Recover 1 Strain when you kill something, and 1 Strain: remove White dice from defender)....By the end, Mak was usually killing 2 figures per turn (No Escape is big here), which meant 2 Strain recovered each round, in addition to any extra surges spent for Strain recovery.
At the end, with 1 mission left before the Finale, I had 1 xp to spend, and didn't know that we'd be able to gain another 2 xp for winning the next mission, and so I purchased Disengage (a good ability anyway), and then Target Acquired after we won the next mission (right before the Finale). If I'd been more patient I would've just saved the xp for Expertise, which I think would've been the better choice.
1 xp: Disengage (3 movement points when an enemy draws near). There's no question that this is a good ability. Perhaps I should've purchased it first, according to comments from many others.
2 xp: Target Acquired (Figures don't block LOS). Meh...I don't think I used it even once, but then I also only had it for the last mission so there wasn't a lot of opportunity for it either.
Mak finished the game with ONE piece of gear: the DXR-6. No armor, no upgrades, nothing. Just a big, big, BFG-9000 (for any of you Doom players!), and it was all he needed. With No Escape and Jeswandi Training, half of his attacks were Focused, and with all that strain recovery from Execute, he really never needed to rest.
What I've listed above was definitely the most damage-heavy build for Mak, and it paid off in the end, but I think that a more balanced build would be this:
1 xp: Disengage
2 xp: Jeswandi Training
4 xp: No Escape
3 xp: Execute (strain recovery) or 3 xp: Expertise (utility), depending on what your group seems to need more
IMHO, Supply Network and Expertise are great if your group needs you more for tech/utility purposes, but they're not really helpful for attack purposes. (In our campaign we had Jyn to do a lot of the utility stuff, so that left Mak free to focus on offense.)
I think Target Acquired isn't really worth it; there are better options available. I think Decoy is just too expensive for what you get: 4 xp for something you can only use once per mission (and therefore just a few times in the whole campaign, by the time you can buy the card).