I would encourage you to read @KRyan's answer, however I feel the need to extrapolate.
There are very few options in D&D to steal a character's agency: you may much more easily disable it than control its mind. This is good, since anything you do to others your GM can do to you.
As a result, in order to provoke others to attack you, you just need to be more annoying that the other party members. Piling on AC and HP increases your resilience, but does not make a compelling target of you.
Thus, your character should be built toward annoying the enemy. Be a thorn in their side. You are unlikely to be able to completely shut them a horde of foes by yourself, but you can leave them only bad and worse choices.
Note: your goal is not to soak up the damage, this is incidental to the task; your goal is to prevent damage to reach your party members. If you can find a way NOT to take damage while accomplishing your goal, it is better.
Thicket of Blades
This is the key stance (Devotion 3) for a tank, any foe moving within your reach, even a 5-ft. step or trying to disengage from combat, will provoke an Attack of Opportunity.
Combine with a Reach Weapon (Guisarme, for example) and the Combat Reflexes feat and you have a solid basis (*). You may not stop foes from moving around you yet, but you instill a sharp penalty for doing so.
If you really wish to stop foes in their track, you can also combine this setup with the Stand Still feat. Damages scale much more quickly than Reflex saves, and the bigger the monster the less Reflex it has (case in point, a Great Wyrm, with its 41 Hit Dice, only has +22 to Reflex), so the feat tends to be worth more in higher levels.
(*) A quick reminder than the max Dexterity to AC column of your armor only limits the Dexterity bonus to AC and does not affect the Dexterity modifier itself.
Bulwark of Defense
A Knight (PHB II) gains Bulwark of Defense at level 3. All the square the Knight threatens become Difficult Terrain, halving foes movement.
Unfortunately... there is no Difficult Terrain for flying foes so it loses value at higher levels.
Great at lower levels, however at higher levels foes tend to be much larger and much stronger making it very difficult to remain effective, and thus it becomes a situational thing.
You are not alone
Controlling the enemy's movement is not your exclusive role, the whole party has to chime in.
Spellcasters, for example, should have ways to control the terrain: Grease or Entangle are examples of 1st level spells which, combined with the natural terrain, allow corralling the enemies.
This is part of the overall tactical effort of the team, as much as you decide who strikes which target, you also have to decide who disable/slows down/holds off...
a group of orcs that flat out ignored the tank and charged into close combat with the casters
Let's replay this with a Crusader with Combat Reflexes and a Reach Weapon placed in front of the group:
- Charges need be in straight lines
- When charging, they take a -2 penalty to AC
- You control 5 squares (2 on each side of you, plus the one you occupy)
- Your party members are behind you
The orcs may indeed pass around you, however this is at the cost of suffering an Attack of Opportunity from you (a +1 Guisarme with Strength 18 makes 2d4+7 points of damage, for an average of 10).
You force a choice on them:
- face you (Good)
- go around (Good: they lose a turn of attacks)
- charge the casters, taking damage (Average: free damage!)
- switch to ranged attacks (Average: they are not as proficient)
a group of zombies with a row of archers that persistently readied an attack "as soon as he starts casting"
You are, and will be, awfully unprepared to deal with ranged attacks. It is not your forte.
Still, there are at least two tactical options here:
- Charge the archers
- Have the spellcaster take cover (at least from some archers) or even dive to the ground if no cover is available
These options are not exclusive.
Charge the archers: there are very few ways to fire a ranged weapon without provoking an Attack of Opportunity, and since you wield a Reach Weapon a 5-ft. step away from you is insufficient to escape your threatened area.
- face you (Good)
- disengage (Good: while they move they do not attack)
- fire their bow (Average: free damage!)
some beasts lead by a druid, who set an ambush to attack us from the rear.
Once again, this is about team coordination. Ideally:
- Move in the midst of the beasts, to start threatening them (you need not charge)
- Have your allies move out
Note that a number of White Raven maneuvers shine here: Douse the Flames (WR 1), Tactical Strike (WR 2), White Raven Strike (WR 4) and Covering Strike (WR 4) allow you to prevent the beasts from making AoO while your allies move, White Raven Tactics (WR 3) and Order Forged from Chaos (WR 6) allow one (resp. all) allies to move out right now.
In a hurry (if you already played this turn), your allies could move without you, simply taking refuge behind you.
In both cases, your party has reset the battle field to get back to the regular configuration where you stand between foes and friends.