in our opinion, sosiel has access to domains which makes him more valuable to a party than daeran regardless o' almost any build am able to imagine for the a$$imar oracle (misspell intentional). it is possible to turn daeran into a decent mounted dual-wielding combatant, and with the nature mystery added via a mythic powha, you will be able to select a mount plus the friend to animals revelation will serious boost the saves o' all party animal companions-- daeran is a useful companion. even so, sosiel is having access to a few o' the most significant abilities in the game via domains and the mythic impossible domain ability makes it possible for sosiel to choose two or three additional domains. favorite domains: animal, community, madness, nobility. have literal not played wotr since release sans a high wisdom character who has access to the community domain.
the animal domain provides sosiel a mount. give sosiel the lunge feat and with his reach weapon, stick him on a legendary proportion dog or boar, then cast frightful aspect, divine power and eagle soul and as long as you got the outflank feat you will be wreaking the battlefield.
alternatively, add one level o' crossblood sorc to the priest o' shelyn and sosiel potential is one o' your best damage dealing companion casters.
late in the game you likely need healing less and there is multiple ways to achieve healing w/o a dedicated healer, so the issue eventually becomes almost moot. aivu is good enough to do party heals for act v if you are going azata. the treasure o' the midnight isles vendor sells 199 scrolls o' most healing spells which functional turns any character with decent umd skill into a healer, but especial nenio with her scroll mastery. speaking o' nenio, you may add mass heal to the spell repertoire o' nenio and ember via loremaster. *shrug* if you do not want sosiel or daeran, ember makes a more than adequate heal replacement particular if you are going azata or angel, so feel free to choose a dedicated front-liner if the priest and oracle fail to meet your needs... but again, sosiel is a brute in combat when proper buffed and mounted plus his domain powhaz make him arguable the most useful companion in the game, though seelah and camellia deserve consideration for a most effective wotr companion award. however, no companion is essential, even if you choose to avoid hiring mercs.
HA! Good Fun!