The harsh 1-2 shift is normal under WOT. In a programmed 2nd gear start transmission, you're on the kick down switch to force a 1st gear start and it will shift at much higher RPM.

The hesitation and rough 2-3 shift could very easily be a broken K1 accumulator spring. The part is cheap, easy to replace, and is well documented on this forum and elsewhere.

Anecdotal evidence time: My 300SDL drove like Helen Keller learning to drive stick when I got it. I found both K1 and K2 broken. Replacing them got the transmission shifting remarkably well despite it being very tired.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]