Indeed, it's worth the effort for the Russians if they can keep both Assad and the powder keg under his feet under control to prevent him from being replaced by a less secular leader. Perhaps even more important to Russia than the preservation of port access and direct trade, a stabilized Syria with Assad behaving himself would mean that Russian energy transit routes to Europe won't face competition from any pipelines sought by Gulf nations like Saudi Arabia and Qatar -- which, not coincidentally, are providing significant material support to the anti-Assad rebels. Assad in power means that a pro-Saudi/Qatari alternative will be shut out of Syria in favor of the current status quo between Syria and Russia.
As for whether this near-monopoly would be detrimental to Europe's energy market, probably not, since Russia is already Europe's top oil and gas supplier, and there's no evidence that having the Saudis or Qataris share that market with Russia would prove advantageous to European countries. Given the ongoing global war against Islamic extremism, perhaps the more important question is whether Europe would want to diversify its energy imports in favor of these two Islamic regimes. With a near-doubling in Qatari natural gas exports to Europe from 2009 to 2010, and with Saudi Arabia and Iran already being the fourth- and fifth-largest crude oil exporters to Europe, according to Eurostat, perhaps Europe's preference is to cultivate some control over these regimes through trade partnerships -- a strategy that Russia has applied successfully to former Soviet satellite states, and that China has exercised in places such as Africa and South America.
The flip side is that Syrian stability also increases the likelihood of eventual pipelines from Iran and Iraq into Syria. Iran, a close Russian ally whose fuel would supply Syria itself via a pipeline through Iraq, wouldn't compete with Gazprom on the European gas market. But America may not like seeing Iraq, a nation on which it just spilled blood and tears for a war and 10 years' worth of rebuilding, buddy up to Syria, Iran and other players in the region, who are at best the competition and at worst a potential security threat.
But with North America set to achieve energy independence within this decade, the returns on such forays into oil-rich foreign lands aren't what they used to be, and trying to break up trading blocks on the other side of the planet is like trying to have a long-distance relationship with a woman who's already going out with a guy in the same town. A bit more creativity is in order, since threatening to get the guy fired, or depriving him of his resources, or just straight-up kicking his butt probably won't work in the long run, if at all.
Putin just took at least one major drama queen and her entourage off America's hands. Accept the breakup, wish them well and move on. She's his problem now, and he's only too happy to take full responsibility.