Couldn't be a better place for Philander to get used to bowling in England. Taunton is one of the toughest grounds for pace bowlers so if he is taking wickets there, he's not just good, he's fearsome and the English players will know it.
Fair enough that Taunton is a batsman's pitch but it's April, it's cloudy and moist the ball will swing and decent swing bowlers will do well but it doesn't necessarily acclimatise you for July/August if the summer is sunny.
I got chatting to some bloke in the pub the other day who goes for Middlesex and we were talking about the SA/England series and he said he was amazed to see Philander plundering Test wickets as he'd played a season for Middlesex a couple of years back and this bloke said he was ordinary whenever he watched him, so it's not as if he hasn't got experience of English wickets/conditions.
The England quicks don't play a lot of county cricket these days but the likes of Harmsion and Hoggard used to butcher batting line ups in early season conditions, especially with Harmison it didn't always mean a lot when the real stuff started.
As for these Paddies, I'd rather not have them playing for England, but it's not England waving money at them, they want to play for England if they see themselves as potential Test players, England aren't stealing them, they're the traitors to their own flag.