I've played a MDPS since launch (valor 100 marauder) and here's my 2 cents on keybinds.
for movement (A and D for strafe). Rebound S
key to basic attack (assault), no more backpedaling. Some advocate using RDFG
since you access more keys to the left side of your hand but I don't find it necessary.
Mouse turning; right mouse button
held at all times to keep camera moving; camera zoomed out to about 80% (change that in the game settings). Combined with WASD, this allows for maximum mobility and situational awareness.
Hold down left+right mouse button
s to move forward while doing fast/complex keybinds or when tunneling a healer and feeling lazy.
Now for keybinds themselves:
I tend to put abilties with similar purposes in the same slots across different specs and characters, because muscle memory can work for or against you. Most accessible keybinds for the most-used abilities (FQERZXC12345); I like using shift modifiers for channeled abilities.
is basic attack (assault), as mentioned before. On healers it can be the basic heal (diagnostic scan), or bubble.
is my 'opener' key. On the mara it is force charge, on PT it's explosive dart, on sorc healer resurgence etc.
is my 'spammer' key, or my most frequently used abilities. On rage mara it's vicious slash, on carnage it is masscre, as anni it's rupture, PT is flame burst, etc
is my 'finisher' key. Rage mara = smash, carnage mara = scream, anni mara = annihilate, pyro PT = railshot; basically your hard hitting finisher
is my execute (vicious throw). For classes that don't have an execute i bind it to something stealth or speed related (force speed, sneak).
for common abilities. E.g. 1- battering assault, 2 - force crush, 3 - obliterate, 4 - retaliate
for your hard hitting/healing channel. E.g. ravage, unload, dark infusion, kolto injection
for primary stun e.g. choke, electro dart, electrocute
for primary mez e.g. roar, whirlwind, flashbang
for defensive cooldowns e.g. wz adrenal, cloak of pain, saber ward, energy shield
for emergency e.g. undying rage, vanish, unnatural preservation
for utility e.g. obfuscate, snare, interrupt, taunts
Middle mouse button
for force camo on my mara, overload on sorc, crouch on operative
Mouse button 4
(on my mouse its the button under my thumb) for CC breaker
Shift - Mouse button 4
for wz medpack
for throw huttball
for special abilities. In my case F1=berserk, F2=predation, F3=bloodthirst, F4=frenzy
) for regen
for mount, ctrl+D
for rocket boost
Shift-mouse scroll up
for mark target star, shift-mouse scroll down
for mark target reticle, numpad 1-5
for mark target saber/flame/shield etc
Hope this helps