Having extensive experience as a hybrid archer, I can tell you that is not the case.
Ok, you will be mediocre in two things, but if you compare that to a 18/24 archer or a 18/21 melee, both attainable at lvl 30, you are in quite a disadvantage.
The wpf in archery truly matters, unlike with crossbows, where you can do well with even 0 wpf... And as a hybrid, you will have problems when going for headshots, and it is better to just aim for the body Also, you need to spend 6 skill points vs 0, which is another problem.
Also, instead of 18/18, I prefer the 15/21 archer hybrid, decent accuracy and melee, at the cost of being a little mosquito when your arrows hit. And with 6 PS not so much, but with only 5, you need around 100ish wpf in order not to glance everywhere (or use blunt/pierce).
Also, low wpf means more repairs, and with the low PD you are better using bodkins, so it is a very expensive build even with medium armor.
Another reason is that even if you hit with most your arrows and then do well in melee, you might get extensive damage to the enemy team, but you hardly ever kill anyone. I still remember getting almost 200 points with 0 kills in siege a couple of times...