How did things go with your re-checking?

I suspect Phex needs its stub to be re-written so that (1) it checks to see if Oracle JRE is installed & uses that java, or (2) checks if Oracle JDK is installed, or (3) continues with the code that's already there to use Apple's Java.
I tried testing this last year but my poor coding skills failed with it. I'm sure someone more knowledgable could achieve it.

I'm wondering if Phex not running on your system is either due to Apple Java no longer being useable on either your newer Apple hardware or Yosemite.

I'm still very happy with using Snow Leopard though realise I will need to upgrade at some point. I intend to take the plunge at some point over the next 12 months or so, though I simply don't like some of the changes which greatly affect my day to day use of the system. The changes will notably slow down my usual methodical way of using the mac. I have an alternate startup drive I might test out first. Up to now I've been testing ML & Mavericks on a VM.

my GTK has been crashing since beginning of last year. Sometimes I'm lucky with it staying open for an hour or two.

There's always WireShare to use, which is the continuation of LimeWire Pirate Edition. WireShare has been re-written to run with either Oracle or Apple Java. But being a Phex user it's probably not your preferred type of program. And WireShare is not as memory or CPU efficient as Phex.