The Power of the AT Icon

I haven't encountered any obvious advocacy of the Empath/Psi Defender in the same post(s) as discouraging the Mind/Empathy Controller, so I'm not entirely sure where the OP is coming from. However a couple points that I don't think have been made - at least not explicitely - on this thread that might explain why such an argument might be made.

The reasons to suggest picking any other primary than Mind have been fairly well explained - you get more use out of the Empathy part if you have something to use the buffs on, so when solo it'll provide greater synergy with a pet. I gather the OPs confusion is as to why this wouldn't also result in Defender being discouraged - why separate the advice between the two ATs.

One reason is simply that the two ATs do play/feel different. Exactly how different is probably at least somewhat in the player's mind, but it's a factor nonetheless. So when making suggestions as to powersets people will naturally split it into suggestions-for-Controllers and suggestions-for-Defenders. That the suggestions-for-Defenders are all equal at best to the sub-optimal suggestions-for-Controllers won't matter if it's Defender gameplay the subject would be happiest with. There's also the concept/aesthetic difference between a character that blasts and a character that mezzes - if you're wanting the blast aesthetic it won't matter that the control version is superior. Anyhow, if someone is giving advice they may not know whether the subject has a preference in these areas and so will cover the bases by providing the Controller advice and Defender advice separately.

There's also the "pure" healer (or healer/buffer) phenomenon. It may be heavily discouraged on these forums, but the desire to create a character that does *nothing* except heal and buff (and sometimes just heal) is still a fairly widespread one among the playerbase. For a person on that path the fact Mind Control may provide superior mitigation than the increased heal/buff modifier on a Defender is simply irrelevant - this group includes those who'll take the medicine pool on an Empath rather than even one decent blast or mez. As sub-optimal and ill-advised as this may be, it can still be a factor in any advice given (either because they're being catered to, or they're giving the advice).

Lastly, the levels at which each power unlocks. While it in the long run it may not matter - once you're 40 you can have anything opened and slotted - there's quite a lot of people who spend most of their time in the lower levels, never getting any one alt that high. Also a lot of people are frequently exemping down for task forces and the like. In those situations it can make a difference and so factors into the decision.

They may not all be "good" reasons, especially from a minmax point of view, but for some people they're significant all the same.