Sub for pre-60: War...always. Also, before 60 you will be using Jinpu and Enpi, both of which are two hits so keep some of the ACC gear on for WS. Don't get dissapointed at the lower lvls, sam can be kinda weak before 30, but when you get zerk and meditate...its over^^
All the WS's after 60 are single hit and have 75% STR modifiers, so SATA WS can be really bad ass if you can stack the STR. /WAR is still the best for your own DoT...but in some situations /thf for closing darkness/distortion may = faster kills...depends on setup. Have both lvled.
Try to always set up 2 skill chains in every exp party, one with tank and one with the other DD. Usually melee TP for first SC and then meditate and SC again with second partner. If the tank is really bad with tp for whatever reason, then just solo TP from meditate. lvl 65-71 can be rough, depends who and what you party with. Gekko only does darkness with nin and pld, so best bet is usually to close darkness with tank and do somthing like distortion with the second melee.
Thiefs were always great partners for me, pretty much from 10-70. They get TP fast and SC well with sam. Also, big thing you sohuld do is get the lvl 50 GKT from riverne site #B01 with clustered tar. I wish they had that when I had lvled sam...its pretty crazy. Occasionaly attacks 2-3 times, can use it for a very long time. That weapon seriously looks like fun, make it a point to get it before you lvl on.