Yes I know shouldn't rely on their web page, but at least is will tell you which rides are definitely closed. I know the scheduled hours for formula Rosso is correct as I have spoken directly with someone at FW but of course it may still go off during those times if an unexpected problem arises.
When we went a couple of months ago the rides were constantly breaking down, closing then opening up again the whole time we were there, so I wouldn't rely too much on the internet. At one point during our visit all the key rides were closed!
Always best to check their website http://www.ferrariworldabudhabi.com/en-gb/plan-your-visit/park-update.aspx for updates or if unsure give them a ring. At present Formula Rosso is not operating due to maintenance getting it 100% for the F1. It should be operational Thursdays after 6p.m. and on Friday and Saturdays after 3p.m. but not guaranteed. Last week when our visitors went Formula Rosso and V12 weren't working but as they knew in advance Formula Rosso wasn't on and they had free tickets it wasn't such a big deal.