in the late game Odin is really just an ok sub (amazing auto heal, good active skill) and not used as a lead because almost all late game descends do a multi hit where they hit 2-4 times in a row which pretty much negates his leader skill. However, yea early game he is a godsend and i actually rolled accounts on my tab until i got him, now i hardly use him. A much more impressive team hp wise is double luci https://www.padherder.com/user/darkstar/teams/#145204 which gets up to 60k hp or double blue odin at 40k hp https://www.padherder.com/user/darkstar/teams/#141555.... currently though my go to team is Bastet/Ronia https://www.padherder.com/user/darkstar/teams/#52598 which admittedly has a lower hp total but hits like a truck and can heal to with 3 hearts and a few combos.

Looks like you already know which of your monsters are great leads, I&I and Pando.

Once I&I is fully evolved her leader skill gives you 2x att and she has 2 row enhance, which means that once she has those awakenings she will give 2x attack and then an additional 20% for every blue row you have (clear 2 rows you get 40% additional)... You should consider running the green bowl dragon because the invade there has this guy: http://puzzledragonx.com/en/mission.asp?m=1150 who will give 2x attack to balanced for 1 turn (I&I is balanced so by running a blue balanced team you can use this guy to nuke bosses), and lacking any other amazing subs he will come in very handy.

Pandora is the stronger of the two leads you have and will clear more end game content because her attack bonus goes up to 4x and her devil typing makes her super easy to get really, really good subs for. So although you currently have a much better I&I team, think about Pandos lead skill when playing I&I and use I&I to farm up good Pando leads like a Vampire http://puzzledragonx.com/en/monster.asp?n=110 . Pando will be extremely hard to use until you have subs that can orb change for her because unlike I&I you have to have large amounts of specific color orbs to run her.