The TB gull wing doors are no worse for rain getting in than say a Piper but not as good as the Cessna layout where the high wing protects you nicely. The worst by far is say a Diamond DA40/42.
In the GT model (not many TB10GTs around since by then the sales were very low; mostly only the TB20s/21s were selling then) the door struts have a different layout and a stronger (600N) strut has been retrofitted to many. But one still needs to be careful in strong winds - as indeed with any other type if the wind is blowing to open the door.