Several things can cause the excessive negative camber. Worn c-arm bushings, worn ball joint, bent strut, bent spindle, bent chassis, as well as the afore mentioned sagging spring. I wouldn't suspect strut mounts so much, I think they would be obviously bad if affecting the camber a lot.

A lot of cars use the strut mounting to the spindle as the camber adjusting point. When my wagon was having camber issues I notched the upper bolt hole in the new struts to be able move it to get a bit more camber adjustment. I only enlarged the mounting hole 1-2mm and it turned out to be a lot more adjustment than I needed to get the spec I was after.

My 4-matic uses a slightly different mounting of the strut to the spindle but I think the same tactic can buy you a bit of adjustment. If your stuts aren't relatively new, I'd go ahead and replace them. They aren't stupid expensive, and well lets face it you can't have struts that are too new. You could notch the upper bolt bolt a small bit or just put them together as-is pre-loading the assembly in the positive camber position before tightening everything up.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff