At 70°, the antenna beam has an attenuation of about 13dB. So without taking into account the multipath reflections, the “best” signal strength difference between both sectors is 13dB.
It might be less.
Example : clutter 1 at azimuth 0°, and clutter 2 at azimuth 70°.
Why not try the following:
sector 1 is facing clutter 1 – 20° (340°)
sector 2 is facing clutter 2 + 20° (90°)
Hence, you’ll have 110° separation = signal strentgh difference of 24dB. Sounds better 🙂 Your antennas will still provide a good coverage, because you’re in the 65° hbpw primary lobe.
Last solution, use only one sector to shoot right in the middle of the two clutters (azimuth 35°). And you’ll have about 4 dB loss at the clutters (you’re slightly out of the main lobe)… maybe less if you have some reflections… and if you use 2 rx div, 4 rx div, TMA ? you’ll get those 4dB back.