Mauler is still good as it is now. Dark light is what makes it shine. However, as it was kind of recently released, it is likely to still be in the nerf radar.
Indra, on the other hand, is in a solid spot right now, and is a really great, skill-based titan. It can be bought for 500 dgems with its kraken version, kraken vajras and yang lee pilot
There are many robots that you can buy using dgems from a 500-700 price:
Cryo leech
Hussar/weber pathfinder
Hussar/weber typhon
Gauss/dragoon bagliore
Glacier raptor
Glacier shenlou
Havoc scorpion
Redeemer lynx
There may be more that I dont recall