Completing a Dominion Match (PvP) with Champion Status yields 40 steel as a reward. Domion matches take anywhere form 10 to 15 minutes, so lets average at 12 (optimistically) including between-game waiting. This means players, on average, earn 200 steel in 1 hours of gameplay. Or, in a 24 hour grind, 4800. Include daily Order/Contract Rewards. That's another 1400, so 6200 steel in a 24 hours grinding completing all methods for steel gain.
So, the most possible steel an player could earn in a day (24 hours) without break is 6200. Non-stop gameplay + order/contracts.
It costs roughly 83000 to unlock all emotes, effects, executions, outfits, and decorations for each hero individually.
So, it would take 13.39 days, or 321.36 hours, of non-stop gameplay without sleep to achieve all unlocks for one hero.
3856.32 hours are required to unlock all content in the base game. That's 160.68 days. Or roughly 5.36 months. Of just gameplay. No sleep included. And lets ignore disconnect issues/down servers or now, and assume you have champion status.
TL;DR Game requires 3856.32 hours of non-stop game-play every day back-to-back without sleep as the fastest way to unlock all steel-purchasable unlocks.
Unless, of course, you buy steel packs to unlock base-game content. Then it only takes roughly $664 to unlock all content.
Silly me, $729, I forgot to include the cost of the game, basic version.
Gotta admit, the most expensive/time intensive game I've ever played so far.
Edit: Hate it, love it, if anything, upvote for visibility so people will know what they're getting into.