I initially wasn't specced into electric slash myself, but having discovered that my cooldown stays at 200% with both Tempest and Phalanx equipped, I respecced into it. And while most folks say you have no reason to fire your gun as a Shadow, I like having the option to whip out the Tempest for a quick finish if my Slash doesn't do the job. Speaking of electric slash, it works great - if only the windup weren't so l-o-n-g on it. But it does give the Shadow much-needed AoE, and even better it's a power you can throw into smoke or down a tight corridor - or even through a wall! - without having to aim. Being able to soften turrets/Atlases through walls is a great ability.
Concerning the passive: according to the Wiki, the power boosts affecting Shadow Strike are supposed to be a bug, so I'm playing as though it's already patched (i.e. not getting too attached.)
Oh, one more thing - in case it matters, I always take Duration over Damage for Cloak 4. This keeps me alive a lot longer, especially when grabbing objectives solo or dashing behind enemy lines for a revive. I also take Damage over Drain since every little bit helps against armor - more than once I've cut a Banshee's throat milliseconds before her nova, and once even saved someone who was about to be impaled.
My Paladin still has a lot of tweaking to do. I absolutely love their "ice inferno" but I don't feel the damage is quite there as compared to my engineers. But the range on snap freeze is awe-inspiring - in tight spaces, you can turn a whole legion of advancing foes into shuddering glaciers.