Just imagining the implications of most of these is amusing.

Initial guesses:

Recon: (Two possibilities)

1. Incredibly useless as computer AI still sees you even while invisible.
Typical situation: Invisi-DEATH.

2. Incredibly hilarious as computer AI are programmed to ignore you as soon as you go invisible. [At most I could see them finishing their attacks but that's about it]
Typical situation: Hit mob or group of mobs. Mobs all start walking to you / Start attack animations. INVISIBLE! All mobs suddenly go into offline mode and just randomly walk around. Rinse repeat for hilarity.

Striker:

Good for those who could use it well. For most it would probably be a lag-fest of speeding into lava, spikes, or other hazards. Would be fun though.

Guardian:

Very VERY good. If you include the increased Hp it's even more so. This would allow maybe 2 or 3 knights with Cutter series swords to just go nuts while protected by 2 or 1 Guardians. The heal would push it wayyy beyond op. Every single encounter the entire party could start with full Hp if they just had some patience.

- - - - -

Conclusions: A team with even one Guardian would constantly start every fight with full Hp. A team with 4 Guardians would be recovering Hp at a ridiculous rate. Battles would be far too easy.

Debianlinux already said it, those things are from Krogmo.

Alternate way: those things aren't unlimited (you cant be invisible all time nor sprint forever), they need to recharge. This special energy they use can't be found on clockworks, only on specific lockdown levels.