Hello there, I´ve played all the characters and I found that each is really fun. But in regards of your question, it depends on the class you choose. For PVE, the best is undoubtly the Titan. The resilience make it harder for you get killed by mistakes. Although all subclasses are equally powerful, I find the Solar the one with the best defense/offense ratio. The Void is a good class for difficult tasks, as many of their skills are based on pure defense. The arc, on the other hand, is the most fun class to play. It´s highly offensive and you can sometimes erase lots of enemies with your "double pulse grenades" and "shoulder smiting". The Hunter is a very cool class, but it lacks a lot in resilience. The arc strider is amazing when it comes to the super, but I find it difficult to master. The void is a common choice, mostly because it can trap enemies (crowd control) and invisibility. But the Solar Knife-Master is a BEAST. The warlock is a class that lost its prestige from D1. The rift hability is useful, but a lot limited. The Void warlock isn´t the paragon as in D1. The solar have some cool grenades, but lost it´s hability to ressurect (thus ending the nightfall strategy of keeping your super). The arc is the best at the moment.

Warlock: Nova Warp/Elements Stormcaller Titan: Fire-Forged Sunbreaker Hunter: Blade Barrage/Trapper Nightstalker