Aw great, another fanboy of Field Marshal Erwin Soleimani. They parade their tanks and missile in Tehran and post videos of missiles left and right but when ISIS is overrunning Kobani all they have to show are youtube videos. He follows US air strikes then drives in claiming he was behind it all. How come Mosul is still in ISIS hands? Oh yeah, no air strikes.
1. Understand that Mosul's population is mainly Sunni Arab which Iran has least amount of influence over unlike Iraqi Shiites or Kurds
2. No body is claiming that Soleimani or Iranian forces alone have beaten ISIS forces. The claim is that Iranian especial forces have been able to train and organize the local population of the Kurds (much like "Basij") in to a force that could fight off and defend Erbil from being captured.
3. Soleimani/Iranian especial forces did not need the bombing of the Western powers to prove their prowess in organizing local forces in fighting ISIS and their likes as they were able to do this in Syria to keep Assad in power and control when the Western countries were fully funding and supporting ISIS and other anti-Assad forces.
4. You mistakenly assume that just because Iran doesn't like ISIS that they are willing to pay any price (including Iranian lives) to get rid of them. That's not true. Ideally Iran would want other countries to get rid of ISIS completely. But if that doesn't happen then Iran has decided to turn this threat into an opportunity for itself where it has now effectively been able to create its own "Basij" / Hezbollah type forces not only in Souther Iraq but also in Iraqi Kurdistan and majority of Syria (or at least It's Shiite regions). It would be long before any central government or foreign force strong enough would be able to dismantle the militia force that Iran has managed to create in Iraqi Kurdistan, Southern Iraq and majority of Syria not to mention the already existing Hezbollah in Lebanon.
5. As far as Kobani is concerned, all you need to do is look at a map and see where Kobani is. If Kobani were to fall the country that would be most directly and dramatically effected would be Turkey which would have ISIS forces figuratively (and perhaps literally) right at its doorstep. Kobani is so far from central Syria and from Iraq that its fall will have virtually no effect on these two countries. But when these ISIS forces start roaming right at Turkish territory then it is what you call the "chickens coming home to roost".
So if the fall of Kobani might force Turkey to either change its support for ISIS if not cause it to directly get militarily involved in fighting them then why would Soleimani/Iran risk their lives to prevent it from falling to ISIS? If Turkey or Western powers are really serious about fighting these guys let them save Kobani.