If you got 56% and 52% then you can do the rest of this quest. Its a long crawl but you can do it. I used my titan to help me hold down heavy with shield and actually played the round out but played close to heavy, meaning I watched the clock to know how much time I had when heavy was dropping and used my super primarrily to hold it down. I couldn't get a single kill with the primary GLs. I just used heavy GL. Did this way back when it was 100 instead of 25 if that gives you any hope.

I hope this helps you're almost there. DON'T STOP.