What is the best Hero and troop formation for battling the Earthen Titan?

Conrad and Wilfred for heroes. Unlocking skills and leveling them up will add to the damage. Have your top two tier whatever that may be and add troops in this order. 5200 infantry, wait, wait, 5200 artillery, 2600,7800,7800,2600 now go back to the cavs and distance and split the rest of your March between the two. You can do 50/50 or 55/45 as they are cab heroes. You will get you best score so far. Higher than sending all 1 tier. This has to do with the hero bond plus how many turns it gets.

Depends on what you have. You need to make the most damage so find your best offensive heroes. Select the troops that fit the best with them (i.e. if they are infantry focused perhaps) The amount of troops that a hero can bring may also affect the outcome, but this may not be as important.

Plus you can alter your Lord equipment to further boost the troops you send.

Its worth making some tests with a few possible combinations to see what works for you.