As I stated above. EPEL did not break RHEL. RHEL broke EPEL, and the higher priority for EPEL is to not terminate support arbitrarily. The real problem here is that RHEL5.5 shipped AFTER libtalloc 2.0 was available in EPEL, and they shipped with an unsupported, forked version of the library, with the same soname. RHEL is being the bad citizen here.
The problem is that EPEL had libtalloc 2 during the RHEL 5.4 days, but RHEL 5.5 shipped with an incompatible library. Because some users already had libtalloc 2 (mostly for SSSD) we can't just drop it from EPEL. So we need to resolve this as best we can.