I'm ~1880-1900, and an Odin player.
I'll go for 5.0x against Loki and Greek, 5.30 against any of the other civs, 5.45 on a map like Midgard where you don't need to make longboats straight away.
Heroic depends on what's going on in the game, but if I were to go fast heroic (something I did all the time before the patch vs Ra), I'd aim for 6.45 or so, though it's possible to knock 15 seconds off of that and be competetive, as long as you can be sure they'll FH too.
In a normal game, Heroic can be anything from 7:30 to 13 or 14 minutes. I'd try to hit Heroic at ~8 minutes on Med for example, then start the valkyries as soon as I start. This is assuming I haven't won the water fight yet. Mythic anything from 11 or 12 to 25 minutes.
You can keep your classical times pretty consistent by varying how much wood and gold you have, so it's still quite easy to hit 5.0x on Oasis as Odin.