All you're saying here is: melee combat = playing badly. And I utterly reject that.
Larian's gaming philosophy says the player can kill any NPC in the game and still move forward within the game and complete any quest or goal. And yet, if a player chooses to favor melee over everything else in how they handle combat encounters, that's where Larian draws their line and says to the player: no, you can't do that, and we're going to punish you for it?
I am not quite sure what point you are trying to make.
BG uses class based system. Party consists of 4 characters. The very point of classes is that they are limited and work best when combined. And while there should be flexibility in possible party composition, it doesn't mean it doesn't have to be some basic level of variation. Still, the poster described a situation where melee characters were at clear disadvantage. Not trying to even the odds (either by drawing enemy out, covering the approach, regruping, using items etc.) sounds like an issue with player rather then system - the benefit of TB system is that players are encouraged to consider their options, rather then clicking on an enemy and hoping for the best. Aside from tha, the ambush player refered to was "optional" he didn't have to allow to get ambushed, and if you rock a full melee team for some reason, getting caught on low ground, with ranged enemies on rooftops to which you have no easy access is clearly not something you want. Making choices valid doesn't mean all choices work just as well in any situation. If everything is always just as good then nothing really matters.