According to SOHR „120,000 fighters supporting Syrian President Bashar Al-Assad have been killed in the civil war since 2011“
https://middleeastmonitor.com/news/middle-east/15876-over-120000-pro-assad-fighters-killed-in-syria

Why is this number unlikely (too high)?
In April 2014 SOHR was speaking of a total „pro-regime“ death toll of 57.500 fighters. So, the statement above would imply that in the last 8 months until December 2014 some 62.500 further pro-government army soldiers and militia fighters were killed. This is totally exaggerated as it would mean that these forces had an average monthly casualty figure of almost 8.000 men.

More interestingly, however, this contradicts another assertion made by SOHR in the same article above:
„nearly 11,000 government security forces and allied militia were killed in the five months after Al-Assad’s inauguration speech at the start of his third term…Al-Assad began a third term last July…“
This figure sounds more realistic and puts the average death toll at 2.200 pro-government fighters per month, which is way below the 8.000 men calculated before.
Assuming the latest average of 2.200 deaths to be true, the highest casualty figure for the government side would be 57.500 + 8 x 2.200 = appr. 75.000.

According to an early report by Nir Rosen and later admissions by SOHR themselves in many cases rebel casualties were declared civilian deaths to demonize the government. At the same time it is not far-fetched to assume that SOHR has been very open to accept rebel claims about „Shabbiha deaths“. Probably many pro-government civilians or state employees (such as ordinary policemen) who were killed intentionally or accidentally by the rebels were denounced by the latter as „Shabbiha“ or otherwise part of the security apparatus.