For the purposes of solo delving as Preservation we will be equipping Brann as a Damage Dealer, besides that we need to select a combat curio and a utility curio to enhance him further, these are the options:

Combat Curios

As a healer, there is no competition here: You are locking in the 464662 and not changing it ever. It is incredibly powerful in letting you transform healing into damage, as keeping Brann healthy doesn't require a huge investment on your part and the multiplier he gains increases his damage way more than any other option would. This curio was specifically designed for solo delving as a healer and achieves its purpose perfectly

Do note that while it is very likely you find this curio at level 1 very early on, you will have to keep doing delves untill you rng into a level 4 one for maximun effect.

Utility Curios

Utility curios are somewhat lackluster, again we need as much help surviving but there aren't any great options here. 455512 is a bit gimmicky but it doesn't really let you avoid a death. The only real option to help you defensively is 446835, with the idea that on half the pulls you will gain the Massive bonus that increases your maximum HP by 5%. This will not only help you a little bit surviving but also increase the damage of fb and chronof via lfm.