So I'm midway through act 2 and came to the conclusion, that the templar is no help at all. Most of the time he uses the heals on himself because he just stands in plague/desecration and dies within seconds (it's hard to increase all resistances with only 4 item slots available). So the templar falls short of everything that would remotely could be considered as support.
Has anyone experience with other followers in inferno and their usefulness? If you found one particularly useful, what skills did you train them?