I'm not really certain how I feel about hybrids. History teaches us that it'll follow one of three paths:
1. Hybrid's aren't good enough at what they do to justify a spot. They can't tank as well as a true tank, can't dps as well as a true dps, and can't heal as well as a true healer.
2. Hybrid's are good enough at what they do to justify a spot. This is great for the hybrid, but starts to call into question whether or not bringing a "true" tank/dps/healer is worth it. After all, if four hybrids can accomplish the same thing as one tank, one healer and two dps, then why bring anything else? Possible hedges against this would be giving "true" classes each something that they bring that sets them apart from the hybrid, but that runs the risk of ultimately making hybrid's like #1.
3. You invert 2 and give hybrid's some sort of unique "something" that they bring to the table (a la RDM refresh). This is the tack most games have taken, which ultimately ensures you'll get at least one spot set apart for the hybrid, because the bonus brought by the hybrid is usually good enough to justify it. However, this carries with it the problem of that bonus eventually being considered "required." If you make content that can be beaten without the bonus added in, then said content likely becomes easier with the bonus. Hence, to keep content challenging, the devs will have to begin balancing content around the assumption that the bonus will be present.
Suffice it to say, I have a dim view of hybrid viability, but I appreciate the goal behind the concept. I'd prefer they add hybrid-ness within the classes themselves, i.e. with the stance mechanics (cleric stance being a great example of how a main healing class can also do some stout damage).
Edited, Dec 13th 2013 1:31pm by Quor