There's plenty that's good about Eureka. It's a beautiful zone, and finally, FINALLY we have an area that's legitimately dangerous. The sense of satisfaction when you make your way solo to a dangerous quest location is exhilarating.
Nevertheless, criticisms that folks have about Eureka are well-grounded. For example, I love the design and mechanics of the FATE NMs - but the fact that elemental strength is not scaled down means that for all but the top few NMs, those mechanics are totally meaningless since a horde can brute-force kill any of them before those mechanics matter. Take, for example, Numbers - over the course of the fight, he summons several Void rifts. Presumably, players are supposed to kill those before they unleash horrors that slaughter everyone - but none of them come even CLOSE to finishing before the boss is dead.
SE clearly planned for players to get the bulk of their Protean crystals by farming regular mobs (most likely, as a side benefit for earning exp), but Proteans flow in at such a pitiful trickle that this is simply not viable. Anemos crystals were supposed to be the "special" ones that you had rare opportunities to acquire. That wound up totally reversed; crystals and exp flow like water by killing NMs. Grind parties would need a HUGE boost in both crystal drop rate and exp for them to come close to touching the efficiency of NM trains, even for very low-level characters. And because of this, lowbies feel obligated to join the NM trains where, for the most part, there's very little they can do except to try not to die as much as they can.
I think most agree that Eureka has its good points, but it also has some pretty significant flaws.
Pretty sure what she means is, "You can't even heal your party members, unless they are close in elemental level to the boss" because they don't take damage when they are hit, they die instead. Which is pretty much true.