Let’s say Assad gets his mini state, a Damascus-Homs corridor + the coastal region. What exactly are the Iranians gaining from that except a big headache? Without the oil, that state is bankrupt from day one let alone the sanctions and the fact that the rich Sunnis for the most part are not going to stay and live there. It is going to be a huge burden for Iran with no clear benefit. That state is going to be fighting Sunni Arabs, not Israel. No, what the Iranians and Assad are playing for is what Alex wants. They want a negotiated solution in which they get something like the French model, a president responsible for foreign affairs and the army, and a PM and government responsible for internal matters. The president of course they envision is Assad. That way they keep Syria intact and maintain its “resistance” foreign policy. If the West agrees to this, they also get rid of the sanctions and Syrian isolation.
What they are doing is trying to bolster their negotiating position in order to achieve this goal. They are hoping that just like the West and the Gulf Arabs finally got fed up with the Lebanese civil war and allowed Hafez to take over Lebanon, the same will happen with Syria. They think that the West will cave in as it sees the casualties and refugees mount and accept their position.
Why is Hezbollah fighting in Qusayr then? To prove to the West that Iran and its proxies are 100% behind Assad and that they can make the war drag on forever. Qusayr is a good place for Hezbollah to fight since their supply lines are very short and secure.
Naturally, the “resistance” is miscalculating badly and using the wrong model. The way the US is going to approach this is the same way it approached the Iran-Iraq war. As Kerry said, any Assad gain is going to be “temporary” because the US will provide the rebels, directly or indirectly with weapons to even things out, but of course not enough weapons to win. After all, what is wrong with making Iran, Hezbollah, Assad and the Islamists bleed for a decade or so? Except of course that it is at the expense of the Syrian people but unfortunately like the Iranians and Iraqis in the Iran-Iraq war, they don’t count for very much.
So basically both sides are playing chicken but with the Syrian people suffering if no one gives. Assad is going to lose this game of chicken because his support base is also bleeding and quite badly as the war goes on and there are strong Western and Arab interests to curb Iranian influence. Dealing with ruthless assholes is always a pain and the Assads are as ruthless as they come.