If the stock market for single player is tied to online and what people are doing in their own games, am I going to be at a huge weird disadvantage if I don't play this game for a few more months?
It's not. There a few stocks that trade on both exchanges but online and offline aren't tied together. They are still fixing the online stock market anyways. It is still closed even after the title update last night.
Are you talking about on Xbox it being closed?
On PS3 I had one day where it wouldn't update prices for 8 hours or so. Other than that, sometimes it won't update for a bit, but it's always updated prices within an hour or so, or if I quit and relaunch a few times. I haven't seen it outright closed, other than perhaps that single day. Though that was right about when online launched so I figured it was server overload.
For Leeroy... there are two markets, one unaffected by other players, and one that is. You should always be able to make money off the first market just by getting familiar with the general max and min for stocks.
The online, I'm not convinced anything matters in it beyond number of shares bought and sold. You might miss out on some golden opportunity like early on where there was a $1 stock so everyone invested in it. But there should be some other cheapest stock that will still draw most of the interest.
Speaking of which, didn't get to play yesterday, but logged in to check my stocks and cash out and make a save point. HAL was outgaining PIS again finally. PIS has passed WIZ, and I expect at some point WIZ will start climbing as well. It hadn't happened as of checking last night though, WIZ was still dropping.
Each time I get my stocks, I put at least one share in all three so I can check the progress since my last stock cash in/save point. It's not clear what number they are comparing to for percent growth otherwise when you just look at the market. This way I can check my portfolio and the percent change is based on a specific moment in time - when I bought the stock.