GC is not a failed skill, however it is a bit of a different build to most high VIT crusaders. A GC crusader should have around 40 base VIT, not 80+ like a standard crusader, there are two reasons for this, first GC does damage in two parts to the caster, first it does a % of the casters max HP, then it does part of the actual damage. the % will be much higher with high VIT, but the second part is resisted with the crusaders skill faith. High VIT also takes away from your overall damage output, this leads to a higher number of casts needed to take out a given mob, which means you will be taking far more damage (mob damage AND GC % damage) than a lower VIT build that has more emphasis on cast power and speed. I have not used a GC crusader in renewal but the best I can tell is that stats are a bit different, mostly in that LUK is now necessary. I used to make millions of zenny with my GC crusader hunting in GH chiv, and look forward to playing another when they are released. Personally after reviewing the new stat features with renewal I plan a GC crusader base stats to look like this:
STR 63
AGI 1
INT 92
DEX 49
VIT 44
LUK 31
the only thing I can think of that might make this not work well is what DEX will really do for the cast time with the renewal mechanics. but LUK raises both ATK and MATK and adds Pdodge and resistance to some status effects. GC uses both ATK and MATK to deal its damage, but your weapons damage will be factored much more than your STR damage, basically GC uses your INT more than your STR but uses your weapons damage for a good boost. GC doesn't take too much to get started either and you can solo farm your way into better gear.
I have also played a battle crusader soloing High Orcs like a fool! it was a seriously slow grind and I had good equips for it, but I did not get sacrifice and stayed as a shield sader, if I was to do another battle type I would go with an AGI spear build. but I have no idea on those
And I have played a support/battle Paladin. They are great fun but really require a party and good equips to be successful. as for stats on a support type crusader I believe you want to focus on VIT and DEX. but I have not looked into a real build for a renewal type sacrifice crusader yet.
A sacrifice crusader is a wizards best friend!