How do you handle progress this late in the expac?

Hi, my guild began HFC in earky february and after a lot of drama that crippled us we finally managed to reach gorefiend mythic. Now, I know the content is almost completely over but we still want to get that gorefiend kill even though it's already pre-patch.

Last week I became raid leader as our guild master went on vacation and it seems things are going to stay like this as the raids are better and faster as a huge chunk of the team tells me. Today we had another 25 wipes on gorefiend and our main problem is we are lacking players, ranged DPS and the randoms we got were as usefull as no one filling that last spot. Luckily we managed to get 19 players from our guild together but for the next ID it's looking bad and I doubt we can do any proper gorefiend tries. The other bosses are no problem as personal responsibility isn't as big as it is on gorefiend...

I wonder how I should handle the situation. Us trying to kill gorefiend isn't about progressing for the kill itself but about testing our endurance as a raid on bosses that are not easily killable. To me it doesn't seem worth it to try gorefiend on thursday if we don't get at least 20 guild mates or people we know that follow my calls in the raid. Does anyone have any advices on how to handle our current situation? This is now ny second time being a raid leader and last time was in HM when I managed my former guild to reach 7/7 heroic in 8 weeks before the guild fell apart...