I think gC_pilot meant 10 op, but it was written 10OP so it kinds looks like 100. That being said, I think 15 SU is too much, that's a 50% speed boost bringing it up the level of conquest and mora. The legion get more fighter wings than the mora and it's a lot tougher than both a them, so that seems easy to abuse. The more I play with it the more it feels like a weaker onslaught that doubles as a fighter platform, which is actually fine once get the carrier skills: you get 2/3 of an astral's fighter bays and 2/3 of an onslaught's power. They also benefit a lot from ordnance expertise as ordnance spent on fighters counts towards the skill. I don't think it would take much to bring the legion to a decent spot, maybe 100 armour so it matches the onslaught, or give it omni-shields by default so it can protect that exposed rear.
Also, sidenote, looking at the wiki it says 15k hull and 1500 armor when that isn't true it's at 18k hull and 1650 armour. I guess it got buffed at some point.