So an interesting thing worth noting is that the healing aspect of the crusader cleric isn't great.
The heal skill is in general not very good for actual healing of HP damage.
The Legion's Blessing ability while interesting isn't great either.
As an example, lets look at Cure Light Wounds, Mass Cure Light Wounds, and CLW with Legion's Blessing.
So CLW normally heals 1d8+1 per caster level (max 5), cast as a standard action 1st level spell.
Mass CLW normally heals 1d8+1 per caster level (max 25), cast as a standard action 5th level spell. It affect 1 creature per caster level, and can do so as long as no creature is more than 30 ft apart.
CLW with Legion's Blessing increases the spell slot used up to a 4th level spell (one below Mass CLW) to heal still only 1d8+5 and does so as a full round action. It requires all the targets to be adjacent to you to actually touch them and can target 1/2 the number of creatures compared to Mass CLW.
Now, where this ability is useful is not in healing but in dolling out what would normally be single target buff spells. Something like Deathward to prebuff the entire party for a fight.
Trying to use the ability during combat probably doesn't work well since you're unlikely to have the whole party adjacent to you when you want to cast the spell.
Ultimately, the most effective thing you can do as a caster for healing is just make sure you carry wands of CLW around and maybe a metamagic rod of Reach for when you're not next to an enemy.
Remember a crusader cleric is more fightery and less healy than your average cleric.
Crusader goes fantastic with Crusader's Flurry...
Who wouldn't want to be a Cleric of Gorum using flurry with a greatsword? Or a Cleric of Magdh using flurry with a scythe?