I guess it depends how optimistic the theoretical is; some theoretical throughputs are more optimistic, while others are more pessimistic. Take Alton Towers, for instance; Wicker Man’s theoretical throughput is 952pph, while the park often exceeds 1,000pph on it, and Thirteen’s theoretical throughput is 1,100pph, while the park got 1,440pph on it in opening year, so those two are somewhat pessimistic theoretical throughputs. Rita, on the other hand, has a theoretical of 1,150pph, and got around 700pph the one time I timed it, and I timed Oblivion at a touch below 900pph both times I timed it on 2 stations, while the theoretical is 1,900pph, so those two have more optimistic theoretical throughputs.
Linking this to Thorpe, Swarm’s theoretical throughput is 1,100pph, and the park comes pretty close to hitting that figure at present (950pph both times I’ve timed it). Ditto with Stealth; its theoretical is 1,000pph, and the park have attained a really solid 850pph on it on both occasions I timed. So assuming that Exodus has a throughput of 1,000pph or just over and the same train design as other Mack coasters, then I could see it getting at least 850pph, possibly 900-1000pph or even higher; if Stealth manages 850pph out of 1,000pph with bulkier restraints and a less roomy train design than Exodus, then I certainly think Exodus could hit that at a very minimum, possibly higher. Matters will be helped even more if the customary Merlin baggage hold is included!
For my money, I think Thorpe does a good job at getting fairly close to their rides’ theoretical throughputs (from my experiences, I'll admit I'm never sure why Thorpe's operations are so criticised; they always seem to do a good job whenever I visit. Do I just get lucky?), so I have no worries about Exodus, personally. The only real significant discrepancy seems to be Colossus, where the theoretical is 1,300pph and the actual has averaged out at around 600pph over the two occasions where I’ve timed it (550pph one time, 650pph the other). From what I can tell, though, 1,300pph is generally seen as quite an optimistic figure for Colossus, what with its compact train design and bulky restraints. This apparently banks on a rolling block setting the ride doesn’t even run, as well.