re: PLAN Type 071 LPD & its Landing Craft
If a Chinese destroyers in the eastern Mediterranean to insert china into the syrian crisis ever uses its AAW capability then china would be at war with someone, probably the US. In any peaceful attempt to establish presence in the Syrian crisis, destroyers and frigates wouldn't be able to do anything other than cruise impotently off shore while the US bomb Syria.
It would be far better to be able to land in Syria and deliver something to impress the Syrians without making the US think china is bringing AAW firepower to screw with the US in Syria.
What makes you think Chinese warships in the Med would have any intentions of getting involved in Syria in any direct way? China is not heavily invested or committed to Syria, and it makes little difference to China what ultimately happens to Assad. China will object to US military action out of principle because its against international law and norms, and will side with Russia to show support and solidarity, but China doesn't care about Syria remotely enough to want to get involved in this mess.
The primary mission of any Chinese naval assets near Syria would be to pass the popcorn and watch the fireworks. They will closely monitor US naval and air movements, tactics, SOPs and scoop up as much emissions and signals as possible for analysis back home. For that task, a FFG or DDG would be far more suitable that an LPD because of the better sensor package they will be packing, and also because they will have a far better self-defence capability than the 999, which only has a single layer of gun based CISW defence, just in case a rogue missile locks onto it by mistake.
An LPD is a capital ship, and the PLAN is unlikely to send one unescorted in even routine training missions outside of Chinese waters, never mind into an almost certain active combat zone. If the 999 is going, than at least one 054A is also tagging along as escort.