I assume you meant Soldier with the Assault.
Medics and Soldiers will always be useful, since they keep the team alive and healthy and supplied with ammo.
Engineers and Operatives definitely have less direct but far more complex combat support roles. Engineers will be valued for the weapon buffs and CP upgrades, while Operatives get lots of cool toys to screw with Engineers' defenses (and Engineers can screw them right back with destroying the hackpad as seen in the Get SMART Objectives video).
It's therefore natural for this pairing of classes to dual-spec in each other (Wraith and I independantly planned to do Engineer/Operative builds with opposing primary emphasis). So the Soldier/Medic and the Engineer/Operative makes sense.
I could see how the Medic/Engineer could work as a team-buffer, that would essentially be the http://www.gamesas.com/index.php?/topic/1181826-master-support-build/page__view__findpost__p__17516681.
Operative... yeah, that doesn't really compliment the other classes well, given the radically different playstyle (everyone else is more about helping the team, the Operative is all about disrupting that).
Soldier/Engineer would be the Master of Blow [censored] Up, Have a Nice Day.
Yes, I did mean Soldier. Too much time spent playing BC2. :sadvaultboy:
In the Ready and Able video we see the following:
Universal - 10 abilities
Soldier - 9 + 2 default abilities
Operative - 9 + 1 default abilities
Engineer - 9 + 2 default abilities
Medic - 9 + 1 default abilities
TOTAL = 52 abilities
I don't know if the devs think 52 is "almost 60", or if there are a few more hidden until release. If there are more I would guess they are Universal abilities.
We must choose 4 Universal abilities with our low-level characters, leaving 16 that can be class-specific. If you want to choose one higher-level Universal ability (choosing Heavy/Light body type may also consume an ability slot) then there are 15 class-specific abilities you can choose.
This would allow you to choose all 9 abilities for your "primary" class, and 6 for your "secondary" class. Or alternatively, choose only 8 for your "primary" and 7 for your "secondary"; both would be very well-spec'd -- the "primary" would be missing only one skill while the "secondary" would be missing only one skill and the rank 5 (level 20) skill. So I tend to think of two-class builds as the way to go.
In my discussion below I am suggesting combinations, not which is primary and which is secondary.
The Support Specialist:
Engineer + Medic
There seem to be a number of "escort" missions ... both will be needed a lot.
The Frontlines Anchor:
Medic + Soldier
Ensuring that objectives are defended.
The Explosives Master:
Soldier + Engineer
A team-player of the non-medic sort.
Tactically I tend to think there should be two squads comprising all four classes, the heavier group working on the main objectives and the lighter group flanking and completing side objectives. All of the above work well with the heavier squad. Those favoring more forward/flanking play might prefer the following builds.
The Ultimate Saboteur:
Operative + Engineer
This is probably the best operative-combo in my opinion.
The Split Personality:
Operative + Medic
A solo artist or the ultimate team player; which do I want to be right now?
The Sneaky "Boom" Guy:
Operative + Soldier
The side passage creator and user.