Including lower-geared characters in raids, basis for.
clearly lowers chance for group to succeed. Requires philosophical shift away from the idea that "it's fine for wiping to not be fun, because it encourages better play to defeat an encounter". If raiding is fun even when wiping may mean the next attempt will happen an undetermined time in the future due to schedules and life priorities, then it becomes acceptable to bring 'undergeared' characters even on difficult progression fights.
...really just a restatement of 'skill cap' argument.
"that which is not forbidden is required"
since 2.1 with epic buffs
smart players realized this, and either quit or adjusted their expectations, for the game and for the relevance of resulting community ideas of achievement, accordingly.
general problem is lack of tolerance for less 'progressed' characters or less experienced players, solution is change in evaluation standards so goals of being accepted can be accomplished without progression, leading to choice
result of "oh this problem is unavoidable" leading to acceptance of chain of problems that result. definitely not an A+ standard of design, even if most other competitors in the realm of complex (not able to isolate a single element with a 'focus group') systems of competitive evaluation and achievement that appeal to unstated motivations are scoring a D-