Ofc it is an issue.
Weapons (and thus rewards) are ordered not just by tier, but also by rarity. Quests are ordered by tier/difficulty. One can easily map difficulty to rarity: easy = common, medium = uncommon, hard = rare; then you can apply unified ordering over quests and weapons. Here is an ordered sequence of pairs tier/rarity over quests and weapons between T6 easy and T7 hard: T6/easy, T6/medium, T6/hard, T7/easy, T7/medium, T7/hard. Thus there are 4 pairs between the quest and its reward - it's a huge distance which makes no sense whatsoever, because no other quests of any tier have a distance from its weapon reward even remotely close to that.
If you take into consideration that a knife is always worse than a gun (and thus additional ordering can be imposed) the situation becomes even worse - because the hardest quest gets the worst possible weapon reward belonging to the previous tier.
And BTW over the years of playing I don't remember a situation where a hard quest of tier X had a common knife of tier X - 1 as a reward. I would not consider current situation exceptional if it happened before.
Overall long story short - this combination of weapon reward and the quest is totally inconsistent with quest reward system, and thus can not be viewed as normal.