There are many advantages for TB combat for a cRPG. Some of them are:
Character Skill vs Player Skill: I feel this is the most important quality to look for in a cRPG. In Turn Based combat, reaction time and "twitch" reflexes cannot compensate for the drawbacks of a character build. In Real Time combat, reflexes of the player can override limitations of the in-game character and hence dilute roleplaying. A prime example of this is dodging/evasion.
Fairness : Turn Based gives no inherent possible unfair adavantage to the AI. In Real Time combat the AI can "cheat" by relying on data/inputs which would not be symmetrically known to the player. Since time in the form of turns (and usually space too in the form of grids) is discretized in Turn Based, the Player and AI are on a more even footing mechanically as the impossible reactions of the AI in real time is not possible.
Balancing: In a Turn Based encounter, the designer has more complete data on possible player actions in a given situation. The designer does not have to take into account the varying levels of Player "twitch" skill while balancing various facets of the encounter.
Tactical Challenge: The designer having more information about possible player actions in a given situation, can up the level of tactical challenge in an encounter. This can be achieved by emphasis on terrain effects, positioning and synergy between different abilities. Since Turn Based is lot more focused than Real Time, the player can also be given a lot more options in a specific combat situation, without overwhelming the player with multitude of options to be frantically selected in real time.