Martina in her prime from 1982-1987 had great groundstrokes as well. So she could hang from the baseline with the best if needed, although she still wanted and tried to come to net alot. That is why she could do so well on clay, a surface you are forced to play back alot.
She was unlucky to not win more than 2 French Opens. The 2 she won in 1982 and 1984 were both won in completely dominant fashion. She had some narrow losses there too though, 1985 and 1987 come to mind, maybe 1986 to a lesser extent. She was unlucky to be in the era of Chris Evert and later on Steffi Graf on clay. Also unlucky the really close matches there didnt go her way, the same way they seemed to almost always go her way at Wimbledon. I think she is a much better clay courter than just a 2-time winner. At her peak I would like her chances to beat Henin and Sanchez Vicario at their peaks on clay, even though both have won more French Opens than her. I am not saying they would be easy for her by any means but I think she would probably have won 6 or 7 out of 10 say.
It is also interesting how some extremely good clay courters like Sabatini and Conchita Martinez didnt even win 1 French Open, while some much weaker clay courters than them did win 1. Martinez funny enough never impressed me much at all except on clay, the one surface I found she was playing at a very impressive level. On other surfaces she was lucky to even have the success she did IMO, but on clay a bit unlucky. It seems the # of French Opens are often not totally accurate to who the greatest clay courters were except in the cases of Evert, Graf, Lenglen, and possibly Court. Alot of it comes down to when you played on clay more than any other surface it seems. Navratilova played when Evert was dominant on clay. Sabatini and Martinez were unlucky and peaked while Graf, Seles, and Sanchez Vicario ruled the French Open. Sanchez Vicario was probably a bit lucky to win 2 titles after the Seles stabbing, just like Graf was a bit lucky to win as many as 4 more after that point. Sabatini's peak was already over when the Seles's stabbing took place.