I have shown that you can't.
I respectfully disagree for a number of reasons.
Only if he had combat focus up will the fighter get a re roll by dropping out of it. Another fighter or some other full BAB person has 3 attacks or more attacks, the fighter only stops two of them. Also it can only be used at 30ft away so archer characters can just plug away. Many melee monster have even more attacks.
Let's pick this apart, shall we?
Another fighter or some other full BAB person has 3 attacks or more attacks
That's nice. Using these "three or more attacks" usually requires what we call a "Full-Round Action". According to "Foil
Action" the entire ACTION is stopped. So they would not get three attacks, they would get 0.
Also it can only be used at 30ft away so archer characters can just plug away.
Thank god this can only be used from 30ft (and later 60ft!). However I question what your Fighter is doing if they are not trying to achieve MELEE distance with a foe. You could be an archer but I believe many if not most people who play the Fighter class see them primarily as MELEE.
Only if he had combat focus up will the fighter get a re roll by dropping out of it.
I assume that in the first round of combat IF your fighter is not within 30ft, and CANNOT move to within 30ft of his opponent, he will use a swift action to activate Combat Focus because that makes sense. Then the second they get within a turn's worth of movement of 30ft from a foe you can bet they would.
To set that up you would need about 2 rounds to do that, one for combat focus, one for the ToB stance since they are both swift actions. Mageslayer doesn't even do all that much since by 13th level a mage has enough in Concentration to just plain cast a spell and not do it defensively. I seems like a waste of feats to me.
I already cleared this up. If you're not within one entire move's worth of distance PLUS 30ft, you can safely use a swift action to enter combat focus. Repeat until you are on top of them. Now use a swift action to activate Thicket. Additionally, I was under the impression that you could stay in Thicket of Blades stance "forever" until you swapped out of it - so yeah I'm pretty sure you do not need to use an action here ever.
What are they going to do now? You can't move without an AoO (throw Standstill into this for easy pwnage). Try to cast a spell? Mageslayer. You're going to do it non-defensively? Hope you can make DC 30+ Concentration checks like they're going out of style. And btw, if your AoO fails to disrupt the spell, you can still hit them with Foil Action!!!
Yes, it is very help but the limits keep it in check.
There are only 2 limits that I would consider in the 'pathetically easy to achieve' category.
1) 30ft (later 60ft) range
2) Hit with a Touch Attack
I think we can show both of these are not incredibly limiting circumstances.
Look at number 1. If you're a level 13 fighter that does not have access to haste/fly as an item/potion/team buff I would have to shrug. But even without those, a base 30ft of movement allows a double move of 60ft which means that 30ft range is *effectively* 90ft. If they try to use a Move Action, Foil it. If they try to do anything else, Foil it. They would need ANOTHER action to do something - in which case next round they'll most likely be facing the same situation. Spells/Potions/etc are totally wasted on the other party's behalf but the Fighter has an unlimited use of Foil Action to keep excessive pressure on.
Look at number 2. If you're a level 13 fighter with 13 bab, decent str, etc. you should have no problem making a touch attack into the mid 20's; very few monsters have that kind of touch AC. Consider that a level 13 Fighter could shut-down any dragon or the tarrasque from the MM on a roll of a 2. That's not "too good"?