Templar for PvP
Pros: Immune to stun, healing skills, holy element effect (most oppenents lack holy resistance), knock down, stun. If you're a human, 5% block passive which is really helpful for swapping certificates, trophies etc.
Cons: Cooldown on combat skills, reliant on magic attacks which can be prevented by magic blockage (no heals, if possibly timed well enough), and also vulnerable to ranged classes.
Best PvP class in arena is Templar with 50% block, 3.00 m-dmg, 60%+ m-crit, 55%+ cast speed. Of course those typical kind stats are extremely hard to achieve and could lead you to spending mass funds on achieving this ultimate pvp class; this is only if you want to create massive impacts during arena but i won't guarantee you a 100% victory.
Samurai/ Mage for PvE
Reason being why I chose Samurai and Mage Is because they play their in certian parts of the dungeon. I believe only mages are great for clearing trash mobs and Samurai is a great DPS for bosses, no could outdamage them whatsoever especially with the awaken katana at their advantage.
To the argument above, I have questioned myself that since the start of the game and there is NO "best class" which is the beauty of this game. As mentioned above I use a 50% block healer myself which works effectly for me in arena because most healers i've opposed in arena get the wrong expression of it make themselves too vulnerable for me. "Your best defence Is your best offence"