I've have played many many sessions of this game, both here on BGA, as well as in person.
I consider this game extremely balanced. There are cards that can overcome the 7 Sector Rocket Removal. Part of the strategy is to make sure that you get 3 or more rockets on the same number that the card can be played on. Yes, it sucks when you see it come out, and yes in the Lightning Variant, there is a strategy to not buy ANY cards if you see it available on the first round. It is a strong card. But if you're smart, and know how to game the game... you can block someone from getting 7's to push it up (in 3-5 player games), or you can just opt to make sure that you can counter it by ensuring you get the same number or more of rockets on that sector when someone rolls (or you).
I love the card myself, and yes it's a strong card, but it's not a "I Win" card. If we're talking about strong... someone getting the Sector 6 Place a Charge anywhere card, with the Level 12 I Win card... that game is on a short timer.
If there was ANY kind of optional game variant that I wish the publishers/developers would allow, it would be a variant to play WITHOUT Colony Cards. This would allow the standard game to draw on a bit longer.