You cant have more than 95% critical hits no matter what you do. Probability that you will successfully hit some monster depends on your dexterity, monster's dexterity and level difference between you and that monster ("color" of specific monster). Also, probability that it would be critical hit depends on yours luck, monster's luck and level difference between you two.
Maximal Bash adds +18% critical hits and 5 LUC points add +1% critical hits. If you make some calculations, it turns out you would need 385 LUC points for maximal critical hit rate (95%) on yellow mobs. Of course, you don't have to reach that to be very good. In PvE, around 50% crit is more than enough.
In this topic, you asked for situation when all players have reached same level - 70, so no level difference between them. In PvP, every opponent has his own LUC and DEX. Probability that you will successfully hit him depends on yours and opponents dexterity. After you hit your opponent, probability that it would be critical hit depends on yours and his luck.
Some players have 1000+ dex or 1000+ luc so it is hard to hit them at all or its hard to make critical hit on them. But, such toons are rare and you probably do not intend to hunt down "dex monsters" or "luc monsters".
As I stated before, 500-600 DEX should be enough in more than 90% of situations in PvP. Also, 500-600 LUC should be more than enough and the rest of your stat points invest in STR.