Ignores Target Defence basically means that you will have 95% chance to hit normal monsters. I think it's a little more complicated than that but it should ensure that you hit almost all the time.
Deadly Strike, is a chance to double your damage, so if you have 20% deadly strike, 20% of your hits will do double damage.
Crushing Blow takes away a percentage of a monsters life, this percentage differs a bit depending on who you are attacking and what weapon you are using. Against normal monsters with a melee weapon it's 25% which is a lot!. Against monsters with huge HP it is very effective. The more you hit, the less effective crushing blow becomes because it only takes away the % of the monsters remaining life.
if you want a more thorough explanation you can go here...
http://strategy.diabloii.net/news.php?id=551#Crushing Blow
I would definitely not put a Gul rune in...the 20% AR bonus isn't worthwile. If you are using Fanatiscism it already gives a good bonus to AR and the Gul won't really make a difference. You also have to take into account your attack speed, so a Shael rune (20% IAS) could be another option, although I think Griswolds Redemption is fast enough. It also Depends on the rest of your equipment what you should put in. I'd say crushing blow is the best, because Griswolds has relatively low damage, but you can also get crushing blow from many other items so 3 Bers is probably overkill. If it where me and I had runes to burn I'd socket 2x Ber and 1x Jah.
