Returning summoner!

[Sargent]

Odin is pretty useless. It's not a bad idea to get him, but he really doesn't see any practical use.

Odin's still useful on HNMs ou can't zerg down with PD/Embrava (i.e. Arch Omega/Ultima, I imagine Odin II). After the SP update I can see Odin > Astral Conduit being a very useful combination for a quick burst of damage on these mobs.

As was said, sub RDM in terms of sub job, working on AF3 is good but please don't consider it the "be all and end all" in terms of SMN gear because it just isn't (and too many people think it is). In terms of Magain stavees, work on a Pet:MAB staff and probably Thunder Perp staff (Ramuh is more or less the preferred Avatar in terms of Endgame for Thunderstorm/Shock Squall), the MAB staff in particular is easy to obtain. Also work on upgrading your Relic Armour to +2 because all pieces are very useful.

[Arcon]

Odin's still useful on HNMs ou can't zerg down with PD/Embrava (i.e. Arch Omega/Ultima, I imagine Odin II). After the SP update I can see Odin > Astral Conduit being a very useful combination for a quick burst of damage on these mobs.

Using Odin can only be done once, as it will remove the Astral Flow status. Unless you were referring to Odin > other Avatar, which would work, but regular DDs will still be preferred for Odin II.