Having seen a lot of DMs that don't factor that sort of thing in (resulting in Ninjas that can't do anything... stupid blindsighted enemies, undead, constructs, etc!), I've seen Ninjas get really screwed regularly.
JaronK
Now we're completely on the same page. I blame uncreative DMs, not players, and really it's the bad game designers who didn't do enough to help newer DMs learn how to make the game fun. I mean you can substitute "Ninjas" with any class really if your DM is not up to task.
See, I see a lot of is how players are playing wrong. To me, that's usually, but not always, garbage.
The way we play, if your Fighter doesn't get to Bull-Rush someone into lava or off a cliff, the DM is the one at fault. Same with Disarm/Trip/Sunder etc.
If there isn't a perfect line of mooks just begging to be lightning bolted at least once per campaign, the DM is doing it wrong.
No, you sure as hell are not going to get to Bullrush-instakill someone every combat, but you sure as hell are going to do it *sometime* in the campaign.
If the entire party isn't left beaten half to death in a cell with only the Monk capable of saving everyone, we blame the DM for a missed opportunity. Everyone is supposed to get their time in the spotlight.
Now to throw this sort of back to the OP, adding BaB, HD, etc doesn't really let your DM be more creative with his encounters, it just makes them raise the bar a little and maybe add in Skills as another possible test, maybe.
Well, now we are in complete agreement.
What I think to be the problem is that many "bad" DMs assume that players should make characters that can meet their threats, but not surpass them by a huge margin. Thus players will make all manner of characters from their own perception of what the DM will throw at them.
Then the DM will throw something at them that can't be suitable for everyone, unless he had a very strict way of telling his players what their characters should be able to do.
I, however, unlike you, think the Tier system takes this into account geniously, as Tier 1 and 2 Classes can easily surprise an unfamiliar DM and do something completely different from what you'd think they'd do.
Here's an example:
[spoiler] I had a DM fairly unfamiliar with wizards that didn't blast (my silly group told me it was an underpowered way to play a wizard if you banned evocation), since I usually played gishie buffer types, and our other caster played a blaster wizard, but the blaster wizard dude asked me to play the wizard so he could play something else.
And so I did, and I made a Conjurer. Now our DM had a kindda silly campaign design where we would be dropped in different campaign worlds, to return the night after, so as we were dropped too far from any major city, the chances, he thought of us getting any reliable information on how to stop this were pretty small. However, as soon as we were dropped a group of Brigands attacked us, and we intimidated them into telling us how far it was to the nearest town. Three days on horseback, in gallop. The DM told us. Well I said, I cast Phantom Steed, and then I ride there, with the halfling from our Party on my horse.
This totally took our DM by surprise and thus he had to change the layout of his campaign to follow this change of events. It was minor, and wind walk would have done the same thing, but it was still so dramatically different from what he was used to, that the high tier class took him completely by surprise.[/spoiler]
Thus Tiers are IMO a great tool for predicting how much the players can actually do. High level tier 1 and 2s can do almost anything, travel almost anywhere and kill almost anything in a matter of seconds. High Level tier 5s and 6s can struggle to deal with level appropriate encounters.
A good DM would alleviate this, and find a strength in everybody's build, and then let that build play out to its' strengths. A bad DM will assume that the players will act within his campaign, and if they aren't strong enough to face his challenges, they are poor optimizers, but if they beat the challenges to easily and generally wipe the floor with his campaign, they are just munchkins.
Sorry, that was sort of a rant.