satori01 said:
As a DM you have to be flexible to be able to handle a Warlock character. You have to accept that with just one Invocation choice you might very well be DM'ing a Nightcrawler type character, Dimension Door'ing all over the place.
DIfferent people DM D&D in different ways. Some DM's run adventures on rigorous time tables, others allow adventurers to explore at their pace and rest virtually at will. Some prefer huge free-for-all battles, others prefer lots of small skirmishes. Some would prefer the emphasis to be on intrigue and social situations, some like dungeons filled with problem-solving elements, and some like hack-and-slash. In short, there are all kinds of ways to play the game, and that means that a usable-at-will ability will have a different level of impact from one campaign to another. That's where each DM has to make his own calls. Flexibility is good; so is knowing when to set boundaries.
For the problem-solving DM, he may want to create situations where a decision about expending party resources has to be made in order to overcome an obstacle. For the hack-n'-slash DM, he may want to keep players from having abilities that allow them to "kite-kill" monsters. In both those cases, they have to decide for their own campaign whether or not a character with the ability to fly or D-door at will is an acceptable deviation from what the typical 6th-level character is capable of.
satori01 said:
Like anything in D&D, (high stats, an unusual combo of spells and feats, etc) it will not "break" the game if you do not let it.
Again, the use of the term "break" implies a certain level of extremity, that we're talking about something that inevitably dooms a campaign to implode. Like I said earlier in the thread, there are many gradients between fine and broken. A DM may find high stats, a spell, or a feat to simply be a hassle, and one way to prevent it from raising his hackles is simply to disallow it.
The warlock is particularly tricky, because he has so few invocations that he will naturally be inclined to use them repetitively in ways that a wizard or sorcerer with "virtually-at-will" capabilities would not. An 11th-level sorcerer may be capable of casting Evard's black tentacles seven times a day, but he can do enough other stuff that he probably won't. An 11th-level warlock whose sole greater invocation is chiling tentacles is much more likely to match or exceed that seven time-a-day limit, and it's not hard to see how that could be a bit excessive.