Honestly, they are all kind of "meh" at the beginning until you hit level 53, which is when you have access to tier 5 heroes. There are some interesting tier 4 heroes like Sorcerer and with the use of a Titan's Soul, you can really pump up their actions. But hero focus is really late game material, focus on hitting 53 until then. Here is a general guide to get you there: https://drive.google.com/file/d/1CtY77u7AwsDUFCfZ3LlrCozlG18i_Elu/view

Shop Titans FAQ.pdfGoogle Docs