It depends on yur approach to combat. Shadow Arts have lots of nice stuff which SUPPORT STEALTHING not GOING INTO STEALTH So the stuff yu will find in Shadow Arts are mostly defensive traits which synergize to applying Stealth to yurself, and some minor sustain, which allows yu to kite mobs around, play around with mobs, focusing on stealthing and reapplying stealth after an attack etc etc. Critical Strikes is meant for a more aggressive approach aimed at taking down enemies faster.For one, yu will have boosted Critical Strike chance, and with proper trait choice, the ability to grant yurself consistent amount of Might, allowing yu take enemies down faster.Yu lose the "defensive" aspect of Shadow Arts, but yu have plenty of Stealth access with Cloak and Dagger anyway, as a result, yu may not really get hit as much as expected.And since yu hit harder, enemies die faster. There are also two key traits tied into Critical Strikes oriented Stealth play :Hidden Killer and Invigorating Precision. A popular build is for players to run full Valkyrie stats (Power, Vitality and Ferocity) and run Hidden Killer to artificially boost their Critical Chance to 100% for the Stealthed Backstab, and for 2s after leaving Stealth.By then, Revealed debuff would have worn off, and yu could use Cloak and Dagger once again to go back into Stealth, and repeating. The main draw is that it allows running Valkyrie stats which feature no Precision to increase yur base crit, which isn't needed because yu basically have 100% crit all the time with yur Stealth based playstyle, and as a result, enjoy better durability over conventional Thief builds. Invigorating Precision is another way to use Critical Strikes, but this time it's just straight forward lifestealing.Using a typical Thief build (probably Berserker or Marauder stats), yu can use Invigorating Precision to Lifesteal up to 20% of the amount of damage dealt by yur Critical Strikes.That's a pretty great form of sustain if yu can ensure the enemy can't keep hitting yu (like going into Stealth every 3 seconds or dropping a Smoke Screen). There is no real right or wrong answer when it comes to PvE, people run what suits them the best.Like I said, it ultimately ends up with how yu choose to approach combat. That's amazing, but wouldn't this make me become a glass cannon?