Overcharge Saber

Dark Charge at 50 is going to heal at least 125. Increasing that by 300% for the amount if times I have it proc is not a bad thing, considering that will effectively give me close to 400 hp per proc. I can see this giving me close to 2k in Dark Charge healing alone, not to mention that a Darkness Assassin using this skill when talented correctly will INSTANTLY heal for 10% of total health on top of that. This may be a bit lackluster for the damagers (I don't know) but don't discount this for the tanks.

Edit: As of Patch 1.1, Dark Charge's healing has been overhauled, increasing significantly and scaling to boot. It only occurrs every 4.5 seconds now naturally, but....my level 23 Tankasin heals for 146 without crit now. At level 50 with Overcharge Saber's effects, I wouldnt be surprised if I got a half a health bar just from procs, nevermind the instant 10% heal. I hate to say this, but love it while it lasts boys....this may be a little too powerful now.

Lets start at the end and go backwards. Hardly a little to powerful healing from Dark Charge. At 50 it's about 400 so bring that to possibly every 3 seconds (completely ignoring the chance to proc part) we are talking about healing for 15 seconds a grand total of 2000 IF AND ONLY IF it procs every three seconds, which it won't. So basically you have an ultra low chance to heal for 2000 hp over the course of 15 seconds. Hardly a desire to nerf this based on that alone. Healers can heal for that pretty much every other second and then you would be lucky to get 65% of the total at that. You would more likely see about 1200 healing after the 15 seconds on a good day.

Secondly the other two charges are hardly worth nerfing for the 15 seconds when they do next to no damage for the proc chance. Lightning charge hits for 60 at level 50 on a 50% chance (does not proc on every other hit btw) and for 15 seconds you boost that to 120 on a 50% chance you are talking about a max of an extra 400 damage. Surging charge is not much different since the proc chance is half of LC proc chance meaning similar damage. If that 400 damage on a 2 minute cooldown is worth nerfing then just remove the ability because it's barely even noticable.

Moving on you apparently didn't read the changes to this ability... They did not keep the 300% bonus on the heal they completely removed it and made it proc more often on the Dark Charge part.

The 10% heal we are talking about what 1600 healing (if you have roughly 16,000 Hit points) every 2 minutes when you use this... included with the above MAX POSSIBLE proc chance of 2000 healing from Dark Charge we gain 3600 HP after 15 seconds... hardly worth complaining about from other classes to mention tank classes that all have much better Cooldowns for tanking than Tank assassins. You are most likely to see during the effect of this ability Being a tank and on use is in the more likely range of 2500-3000 total healing even with more hit points. If you see more then all the better but on most cases and the average you will get that. If you get really lucky you may get the 3500-4000 range which would STILL BE after 15 seconds divided between 15 seconds we are talking about a super massive 267 healing per second. WOW oh WOW is that mind blowing right? and that is with 4005 healing.

Lastly for Chewbee:

You get the 10% heal by being a tank and getting two points in the talent Hollow. Force Shroud is also 3 seconds long until you get Disjunction just for reference. The ability isn't originally 5 seconds.

For a two minute cooldown this is not very useful. While most of your abilities will be hitting in the 1000-3000 range in the early 50s, this gives a very small increase in damage output as charges do not do very much damage by themselves (And dark charge's healing is laughable)

Though i'm not 50 yet, so this is just speculating.