For me, hardcore has to do with your attitude towards a certain objective. If your guild is strict on attendance, demanding of how you spec your character to the tee or have an extremely militant raiding environment where it is always serious business... I consider this "hardcore". In my opinion, you don't have to be "hardcore" to complete the hardest of encounters.
When I played World of Warcraft, my guild was able to clear every Heroic Mode content but we did not consider ourselves "hardcore" because we only raided 2 hours a day for 3 days a week. That's a total of 6 hours per week. Because of this, we considered ourselves casual yet skilled enough to compete with "hardcore" guilds for server first with much less time invested. In fact, we were extremely laid back during raid times and usually joked around in ventrilo during progression.
For the sake of this discussion, I will use World of Warcraft references. Fights such as the "big bosses" like Lady Sinestra, Ragnaros (Cataclysm version), Kil Jaeden, Lich King and Yogg-Saron are examples of hard encounters that require coordination with your raid members. For the less competent players, this can be considered "hardcore" content because they are end-game encounters that would not be easily taken down by less coordinated raids such as PUGs. You don't have to be "hardcore" to tackle these bosses. Just understand the mechanics and do what you're supposed to do and your raid should be successful.
RNG drop rates, farming tokens week after week and and other time sinks are not what I consider "hardcore".
I appreciate having different difficulty modes for raids such as Normal and Hard. Hard mode is meant for players to challenge themselves further and I think casual gamers should not complain about this because that's what normal mode is for. The gear is slightly better from hard mode encounters and the players who complete this content deserve it because, well, they earned it. I don't think everyone should have the same gear because that takes away the sense of accomplishment for those who were able to tackle the harder version of a content.