Yeah, using a second platoon is going to make your commander level gap huge. We've been talking about this since the first event...shame you weren't here for all of that.

Since the event tiles only give 100 XP each no matter how high your commander level is, what you can do is use only your highest level tanks from both platoons for event battles and you won't be missing out on very much XP for those newer, 'better' but lower leveled tanks. Then swap them back in when you do lower risk maps that give better XP. This probably won't fix the problem entirely, but it will let you advance farther than just slamming those newer tanks into the grinder.

Alternatively, you can just try to minimize your commander's progression for the duration of the event. Limit yourself to PoC, event tiles, and get your daily missions done on Angora. MAYBE do invasion tiles if you're not too close to another commander level. You won't get the whole prize, but if you're in a bad enough position that you're worried about getting ANY of the event tanks, this might be the way to go. Judgment call on your part, here.