Just test this skill , AGAIN . It seems that Holy Freeze only cancel the ANIMATIONS of other Auras , not the EFFECTS of them . Most of the Paladin 's Auras still have their effects active even if there is no Aura's animation , example : Might , Holy Fire , Blessed Aim , Concentration , Holy Shock , Defiance , Vigor , Salvation ...
I dont even know how to describe this mechanic lol : the progammers programmed the game this way so that the game can generate less animation when 2 Auras conflict ? lol —The preceding unsigned comment was added by Daywithoutgames (talk · contr).
I can tell you that with identical auras, the one with the highest skill points gets to dominate, regardless of the side you happen to be on. Other auras, however, get to be active, otherwise there would be even less variety in paladin builds. I believe that if they're equal, they cancel each other out.
For the second part, it's similar to that thing about if you have multiple elements of damage, but you don't see them all at once. Auras typically alternate in being displayed when multiple auras are in effect, like having Shout, Battle Command and Battle Orders active at the same time. The effects are all there, the graphics aren't displaying all the time. It was likely done for the reason you mentioned since this game is supposed to run on a 233MHz computer with 64MB RAM.
EDIT: I see what you mean now, and I'll stick to my statement that the auras are just graphical notifications, not the skills themselves. They keep those number separate because they generate less stress than the graphics. ;)