I've done TT at RD countless times and very few times was it down and when it was it was for a few minutes so still a short wait in comparison to if you went later. Plus later in the day its more likely to be down for longer periods of time since the rain generally occurs in the afternoon.
On the other hand Soarin' does not have near the waits it used to plus its very easy to get as a 4th FP+.
I would have a FP for FEA and RD TT or I'd have a FP for TT and RD FEA.