The characters come across as incredible posers, and the re-enactments are about as heavy-handed and schlocky as something from the Hallmark Channel, while as blunt as a brick wall.
If they're trying to be convincing, they failed--failed utterly. You'd have to be really, really, really drunk to want to watch more than about 10 minutes at a time. You'd also have to be extremely devout to believe what's being shown. These actors do a poor job of convincing me that they're human, much less that they're portraying real people.
I have to ask:
Why was this made?
Who was this show made for?
Who could possibly benefit from this?
Someone paid good money for this, and I cannot imagine why.
UPDATE: I did some research into this project. It seems the idea was to have actual exorcists (or people who believe they are) tell stories about what they've dealt with. It was originally intended as a serious interview show. Then Eli Roth was brought on board, refilmed the whole discussion board with Bishop Long and the people he picked, and scrapped everyone and everything else to make it /his/ show. In the process, of course, anything remotely interesting was lost, as was anything of substance or integrity. Also, all the "exorcists" now only tell stories that are 100% in keeping with catholic doctrine and mythology. What a load of guano!