I've only had the game a few days but this is what I've learned: Play to your titan's strengths. The titan I've mainly been using has been scorch. Since scorch has a massive instantaneous damage, with the primary shot, the gas can, and the firewall. Also, stick close to cover so you can pop in and out with your reloads. I found that it worked best staying behind the more aggressive titans like ronins and legions, while firing your thermite over their heads.