In case of the Druid's Revenge that I described, the very idea behind that feat is to buff the casters abilities to dish out way more magic than would usually be possible, which is why it comes at the expense of the character dying (he literally crumbles into ashes after his astral power is expanded or 1h has passed).Yeah, I can tell that both of those "destroy at level one" iterations scream like Pun-Pun; a thought exercise that at best uses RAW (rules as written) as maliciously as possible and something that will not make an appearance in a game because the DM can just go "no" or actually use RAI (rules as intended) to say that it doesn't work that way.
You can stack that with other, completely normal, benefits for casters (one of which allows you to increase a spell's range up to the horizon) and these synergies are, what makes this so ridiculously powerful.
You can tailor-make a character to use all this at level 1 legally, however said character wouldn't be good at anything else, which is powergaming to be sure, but nothing prevents you from reaching this goal naturally through regular level-progression eventually with a standard Druid of the same class.
It's not abusing "rules as written, but not intended", it just uses very strong synergies between different benefits and abilities, that stack exceptionally well.
Ironically, this whole hubbub isn't held back by the rules (or "rules as intended) so much as by the lore, since a druid would never make light use of such an ability, precisely cause it would create such a massive effect. That is to say, to even just consider using such a tactic, there would have to be some really apocalyptic things going on.