Had a WFCO8955 in my last two TT's. They never failed or ruined any batteries. But, charge times, that's another story.
Put up with the WFCO in the 1st TT because I didn't know any better. With the 2nd TT we did a bit more dry camping and really got tired of running the generator 3 hours just to get a minimal charge (batteries discharged to 12.2v; 18 amps of initial charge current @13.6v).
As a test, temporarily connected the WFCO to a pair of discharged batteries (12.0v) via 3 ft. of 4 gauge cable, hoping to activate bulk/boost mode. No go. Got a whopping 2 amp increase in charge current--20 amps.
Installed a new PD9260 as a primary converter. Left the WFCO8955 installed as a secondary backup. The PD9260 outputs 55-60 amps of initial charge current (bulk/boost mode @14.4v). Getting the same charge with the PD9260 in just one hour that used to take the WFCO8955 3 hours.
For those that do any kind of dry-camping, it's really hard to ignore these kind of performance extremes.