I split 4/4 tac scan/fitness or 5/5 passives fitness. Wanted to max it once for the walls hack on the Infiltrator since I need grenade capacity on him instead of Geth Scanner (been trying to set every grenade class for Geth Scanner lately, so far so good for Stimpack/RM on the two infiltrators, but the for real grenade kits it's easier said then done. I want my cheese capacity
), but wasn't working out as well as I thought in that one match. Shouldn't of respeced out of wall hax so fast after only one match. Anyone have much success or fun with wall hax?
And splitting full Tac Scan for les passives is a no go at all. Since you still end up doing the same weapon damage, only now your teammates also stand a better chance of robbing you of epeen powers. So I know this won't fly with certain BSNers. Yes, you know who you are.
So yes, if it's not for Wall Hax, I see no point at all in maxing it. Besides, the debuff you get with just 4 points in it is quite massive enough as is. And I only really use it for bosses in my Gold matches anyways. Though I'm thinking if I should just max fitness and drop it now because of this topic? But I still don't see much worth in just maxing fitness shields via the last fitness rank. He's got plenty of shields as is. And I feel more of a team player debuffing the big bad bosses that wet the pants of my poor pugs I play with... or Banshees wetting my pants. 
Now my Quarian Soldier on the other hand, I see nothing stopping me from maxing it out.
And since he uses no grenade capacity, Geth Scanner can be used on him so no need for Wall Hax ever. Max debuff all the way!!! ... Though now that I think of it, maybe clip pack gear would be better? ie. I'm thinking Typhoon.