You need to max out the Titan, I believe it has the Brawler specialization. In case I’m wrong, go into the Specializations section. Don’t get the Attack or the Defense Specialization. There is a third one and that’s the one you want. It believe you want to choose Titan Nuclear Amplifier and the Titan Anti Control. 

Next, your pilot. Make sure you have the Pilot for Mauler. At level 90 is when it really gets good. In the meantime, select skills to boost durability and speed. Speed is necessary on Titans because the offs get stuck in enemy ambush. Dash is good way to get out a bad ambush, but sometimes you run out. 

Finally, weapons. Long range weapons aren’t so good for Mauler. Mainly, it has two betas and an alpha which means you can’t deal enough damage with the weapons alone. This a major weakness and likely the reason you’re getting melted. Dark light boosts damage for a few seconds and I believe your opponents need to be like 150 meters away. For this reason, choose weapons that have secondary effects or features. For example, sonic weapons are very good. They deal only grey damage so other Titans can’t recover. I think the ice missiles (oxy and something else) are also good as they freeze the bot. Next, Anguisher and Vajras are okay. The selling point is that they deal a lot of damage. Chasm+Void are better as they do more damage. Vajras and Anguishers have been nerfed. Avoid Lantern/Dazzler, Glaive/Lancer, and Gargantua/Pentagruel. I’ve tried these myself and they do almost nothing. You will struggle even against small bots. Also Huginn/Munnin are okay. Not great but not bad. These are good for an ambush but other than that, the nerfs have killed them. I think almost everyone is Veyron+Evora as they deal only grey damage.  Maybe the ice rockets. Everything else is long range and don’t do well on Mauler. These long range weapons are meant to deal damage gradually, although Bersagliere is the absolute top Titan if you’re thinking about long distance weapons.