Team Builds are a lot of fun, excellent exercises in tactics and strategy. They're fun to read about and see how they work, and they are very interesting to see put into action. I do not dislike team builds for this reason, not at all.
What I dislike about team builds is that with a team build, there is little flexibility in both the play style of the player and little tolerance for a player lacking one or more campaigns, lacking high title track ranks, or not being as far as others in some campaigns with some characters. To a slightly lesser extent because of the cost of armor and runes, builds requiring those can be draining on resources too.
For instance, todays FoW event had me running like mad with my Ranger all over on Thursday evening. I had to get a pet, find like two skills, and then I needed to actually go ascend and get the Ritualist secondary. I jumped at it, but eventually I got exhausted and tired of playing my Ranger and decided it wasn't worth it.
In short, builds are great things if someone is already through all the campaigns and has all the stuff to do them, but for players who are still working their way through PvE, the ability to use character Builds is hampered, and being expected to in order to go with the group somewhere is kind of depressing.
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One other thing about builds in general is that I don't feel you can just hand someone a build and then expect them to use it perfectly outright -- they need to be taught to use it, or practice its use. Efficiency is good, but not at the expense of the fun, because that's what the game's really about. Right?
That's just my stance on it, no offense to anyone or anything through this, I just wanted to clarify my opinion on builds.