I usually play deception sin and I have to agree some of OP's changes are really really needed.
1.First off assassins training needs fixed then maybe I could actually hit 5k medal kinda like how every other dps spec can or at least it feels like according to scoreboard.
2.Saber conduit internal cd needs to be removed, its not even that good with 25% chance to proc via surging the least they could do is remove Internal cd.
3.Blackout buff needs to be raised to 12 secs, 6 secs is Way too short
4.Spike needs to not trigger GCD aside from that this ability is fine.
5.I Really really really! like your idea about force speed becoming a shadow step and anyone who plays a sin should to because if you have played a sin you would know force speed is a crappy gap closer it really is, you can get stunned/slowed/cced while your sprinting and then you have to wait not 10 not 20 but 30 freaking seconds before its up again. Making force speed a teleport behind target is the most brilliant idea I've heard on the assassin forums and would greatly help with gap closing since it would be a guaranteed gap closer not a control based gap closer which totally relies on your enemy to be too stupid not to stun/slow/cc you while you pop it. Not to mention melee is already fairly weak in this game in comparison to ranged, don't try and deny it. It would make assassins a bit more viable to play and no it wouldn't be OP at all since it's still a 30 second CD, to make it easier on devs coding it you could just make another ability that does shadow step but shares the same CD with force sprint it would be easier to code and would work just aswell.
Now here's to hoping bioware reads this thread.