MB's use Cross-Drilled rotors. I had cross-drilled rotors on my 92 Integra, my 94 BMW 325i and my ex gf's 98 Civic Ex and on my best friends 92 Lude and they all work perfectly fine. It might depend on who you use, I used Powerstop rotors but I might change over to powerslot. If anything, just get brembo blanks and more aggressive pads. But your shop was full of shit or maybe the companies that they've installed are crap.