I need a good all round scarab class, any suggestions ?
Also is it best to use suppressor or not ?

I Play with Energy transfer, stealth enhance, and mobility enhance
The silencer is totally worth it as well as extended mags.

I use the same except I use nano recharge or armor enhance instead of energy transfer.

Scarab without any addons, Energy Transfer, Stealth Enchance and Retriever

Primary: SCARAB-laser sight, extended mag
Secondary: Majestic
Explosive: JAW
Armor: Nano recharge
Stealth: Stealth enhance
Power: Weapon pro

works every time.

I use a couple different ones.

Scarab: ironsights, extended mags, supressor
explosive: frag grendade
energy transfer
blind spot
retriever

second one:
scrarab: iron sight, extended mags/grenade launcher (I switch them out sometimes)
explosive: frag grenade
Energy transfer
cloaktracker
weapons pro

third one:
scarab: reflex site, extendedmags
Explosive: jaw
energy transfer
stealth enhance
aim enhance

Just some suggestions, feel free to take what ya want and change things around from everyones ideas, theres plenty of options

My loadout looks a little like this:

Scarab; Reflex sight & Extended Mag (No suppressor, it weakens the gun making it impossible to kill from a distance)
Frag Grenades

Energy Transfer
Stealth Enhance
Retriever or mobility enhance

With Frags you can just throw them at random when you spawn on most levels & score kills now that they have been overpowered. Also, energy transfer is the difference between being decent & winning 1 out of every 3 IA matches you join in, I don't care what anyone says I never lose to someone that doesn't have it equipped unless they are spamming armor, and I don't adjust my tactics quick enough. Also, Retriever just makes the game a lot more fun for me. 4 kills get an orbital strike & 6 get a gunship. Also I've learned to love the max nano suit. AT first I hated it, it wasn't until they nerfed it that I learned to use it properly. The support bonuses just add a lot more to the experience I would say, and on some maps they are essential for the win. Just remember that this is with upgraded perks. Also, the suppressor has a dramatic effect on the scarab's damage at a distance. there is a lot of up close shooting where it has little effect, but nothing is worse than running out your clip when 4-5 people are closing from every side. Suppressor doesn't do anything w/ maximum radar, which I always have on almost, so you suppressor guys have a false sense of security.