It appears as if both the Assad regime and Daesh possess the military-geographic advantage of interior lines in the Syrian Civil War.
Such an advantage usually allows a warring party to move its mobile reserves around and strike at several places in succession, while enjoying local superiority.
That's what we read about Daesh, but I cannot quite recall much equivalent offensive action on the operational level of war by the Assad regime. This is curious; it might point at Assad having a long-term strategy that's not built on a string of local successes at all - even though on the simplistic maps lots of opportunities seem to be enticing.
Another interpretation would be that the Assad regime is lacking the capacity to strike with mobile reserves - either because they have no mobile reserves, because they don't dare to commit them due to defensive reserve needs or because the morale of the forces is insufficient for offensive actions far away from a specific region.
The latter may be the most true; there were plenty reports about how the Syrian army disintegrated and was largely replaced by centrally funded Loyalist militias. Such improvised militias are notoriously incapable of long-distance operations. The fighters of militias usually stay with their families overnight.
On the other hand, the strong foreign support for the Assad regime (Russia, Iran) and the substantial foreign hostility especially against Daesh (bombing campaign by the U.S. and Persian Gulf dictatorship air forces) as well as the stupidity of Daesh in regard to adding opponents needlessly (attacking Iraq, alienating supporters and neutrals with destruction of cultural and archaeological artefacts including mosques) point at a possibly long-term strategy with intentionally little offensive action (and thus attention of unfriendly foreign powers) by the Assad regime's forces (including Hezbollah, which appears to have suffered badly).
It would be quite interesting to learn the actual strategies and capabilities of the warring parties in Syria instead of the event-based news stories. One could assess the civil war there and its ramifications much better. Foreign policy about Syria without such an understanding is blind meddling.