I have erased my character because of a big mistake, and restarted a new one last night (short night...)
my first shadow warrior eated 45 shadow veil rune to be 100 % invisible, it was a very very bad idea.
the regen augmentation is huge on shadow veil, it must be avoided at all cost, and the invisible % go up by itself anyway, just by leveling the character and pumping astral lord focus and lore.
so, I think only one rune for shadow veil is enough, and every gear that increase shadow veil must be avoided, like + ... to all combat art, + ... shadow veil, aspect : astral lord + ...
now, I am level 17, and my shadow veil with 1 rune has + 5,6 % regen and 52% invis, and below I see that with 2 rune the regen is + 8,4 %. I was over +65% regen with my last character...