Most solid duo for Kunark and Velious

[Cogwell]

MAG/SHM: High DPS, No Snare, No CC, No Pulling ability.
substitute CLR: less DPS but some Pulling ability and rezes.

NEC/SHM: Slightly lower DPS than the above, but with snare, CC, and Pulling. If pet tanking, the pet is slightly less sturdy. Works best when Fear kiting.

RNG/SHM: Decent DPS, extra utility in snare, various ranger abilities.
substitute CLR for less DPS, add rezes. Both characters use mail, which can be a downside.

SK/SHM: Moderate DPS but the ability to be full functional in any location, and the ability to take down tough mobs the easiest of all combos.
-preluclin, you dont really want to substitute CLR for SHM here as the SK simply can't kick out enough dmg to make it worthwhile.
-substitute WAR for slightly more damage and tanking, less pulling ability, no snare.
-substitute PAL for more buffing, less DPS, moderate pulling ability, stuns instead of snare.

MNK/SHM: Decent DPS, pulling ability, no snare. MNK can mitigate well but can only produce threat through damage, and therefore SHM will have aggro a lot.
substitute CLR for less DPS and rezes.

WAR/CLR: Moderate DPS, decent starter group to build around. No Snare, CC. Relatively boring. Can Substitute DRU for CLR for added DPS, ports, snares, invis but less heals, no rezes.

SHM + any DPS can be effective but not as effective as those above.

Various combos with ENC can be effective, including CLR/ENC, DRU/ENC, PAL/ENC, but are higher risk and harder to pull off.

Various combos that include aggro or fear kiting with a NEC, DRU, or WIZ in addition to any other DPS can be effective but not as much as those above. They need space to operate which leaves out dungeons, primarily.

In essence - there is no *Best*. Each has pros and cons. Have fun!