Power tiers are more fungible than people often make them out to be. One thing to remember here is that WE DON'T HAVE TO USE JUST SS as a herald. I suspect it would actually be much more effective to use many less powerful heralds whose powers are better suited to fighting Odin. I think it could be done with 12-15 heralds. You need 6 or 7 heralds with high damage and durability to act as cannon-fodder (SS, BRB, King Hyperion, etc.) The remaining heralds should be either high-end telepaths who could collectively mind-rape Odin (admittedly, this begs the question: how many Moondragons, Cassie Novas, Exoduses etc. does it take to mindrape Odin? I suspect that 6-8 top-class telepaths could do it via mindlink), or high-end magic-manipulators who could collectively depower or restrain him (Loki, Enchantress, Strange, Vulcan, Warlock, etc.)
A THIRD strategy that would reduce the number of people it takes is to use characters whose powers can stack. Mimic, for instance with the powers of Darwin (adapt to magic), Multiple man, and three others might be able to last quite a long time against Odin, long enough to give team members a chance to launch an effective attack. Another example is Starfox, who isn't that powerful by himself, but who could probably raise Gladiator above herald level with his emotional manipulation.
So: here is a possible team:
1-2) Quasar and Superman (Quasar amps Supes with yellow sun)
3-4) Starfox and Glads (Eros amps Glads)
5) King Hyperion
6) Silver Surfer
7) Black Adam
8) Vulcan
9) Cassandra Nova
10) Moondragon
11) Exodus
12) Shaman X-man
13) Xavier
14)Martian Manhunter
15) God-like Cable