As some of you know I spend some periods on characters and I have two almost max level multicrafters. So, let's say, I speak with some insight on this matter.
Since its implementation ten years ago, herbalism has been a great pivot for many things. For instance economy: selling herbs or potions for the first levels can be extremely useful and quite fast as a way to gather money for equipment or else. It has led also to some RP stories, with rivalties, friendships and else born by a cauldron or while picking herbs. It has also allowed, in time and with some longer time-span, the acquisition for some characters of some spell-like abilities which has allowed either to replace a caster in a party or to wholly solo some dungeons. This is why, for instance, apart my two multicrafters all the characters I've played (all but one) have reached some 20-30 levels in herbalism, and it was not really because I purposedly tried to do that, but because unlike other crafts the materials for herbalism is something you find while travelling here and there. Furthermore herbalism deals with a consumable type of equipment, thus there will always be demand and use of it, whereas once a character has bought a specific sword, bow or armour won't buy a new one in a long time unless some accident happens.
Yet, other crafts have DCs going up to 70 while herbalism used to have 40 as a peak, just in terms of overall balancing I reckon this change was long due. I'm pretty sure that if some DCs result not well balanced our developers will tweak things (it has happened several times in the past, I don't see why should there be a problem it wouldn't be fixed now). On the IC aspect of the matter, one can interpret it as they wish, considering the most "knowing" characters are aware that which happens in the Mists can change suddenly (I mean whole nations vanish or move, let alone if some material can change its behaviour).
I understand those who thought having arrived to a point where failure couldn't happen now are upset. That will happen also to my characters, call me mad, but I'm glad for it because it means there is a new challenge to face. Last thing: crafting, in general, can be time consuming and requires dedication, but when well thought is a different source for RP. I'm confident in time this change will be appreciated by most.