The Assad government has and will continue to wreck havoc on Syrians at a far greater rate and with greater efficiency than what the militants can do. The aerial barrel bombs that are dropped constantly on civilians is the leading killer of Syrians and the main reason they are fleeing; children accounting for a large proportion of those killed.
The Syrians rose as a lot of Arabs during the Arab spring and four years later, they are still being punished for doing so. There is no way to accept Assad as part of any ongoing political solution as Russia is envisioning and pushing for. As we saw in Iraq, once that iron grip hold of power is loosened, there’s no way to get it back.
Assad has no role going forward and deserves the same fate that befell Saddam. The sooner Russia accepts this outcome, the more effective these talks can be.