That applies to all classes, it isn't Warrior specific. Understanding the strengths/weaknesses of each class is part of what defines a good player.

Warriors have a number of weaknesses that are harder to offset than other classes. With the right gear, understanding of the class, and good teammates, these weaknesses will be overcome.

A skilled Knight can overcome the same weaknesses of a Warrior in EC gear, and they do not need to rely on having good teammates. Knights are better at tasks like pulling, which enables more low man group compositions. The only thing Knights end up lacking is Warrior Discs, which are only needed on a small percentage of content.

The other thing people forget (due to everybody being well geared these days), is most content wasn't designed around characters with end-game droppable gear (and/or raid gear) at level 30. While a Knight does do less DPS than a Warrior, the average P99 Knight is going to be much better geared than what the developers balanced the content around. P99 Knights are probably doing more damage than a Warrior in the expected gear at level 30 (something like Minotaur Axes and Crafted Armor). This means P99 Knights are pulling their weight DPS-wise when you look at the gear the content was balanced around.

That is the difference in the end. For most P99 content, a Warrior isn't as good as a Knight.

When you are level 60 and have other experienced players farming content with you, the Knight's advantage will wane. Many players do not get to this point, however. A lot of Warriors are alts that get extra DKP thrown at them, and they get stuck somewhere before level 60 forever. This is due to their weaknesses, like not being able to solo well. Any time you can't find a group for your Warrior, you probably aren't going to be leveling them. While a Knight does level slower than a Warrior, the Knight's ability to solo well will often times offset the Warrior's XP per kill advantage.

Warrior is just simply a terribly designed class
Unfortunate

How would you fix Warriors with the fewest changes possible? I've heard people suggest giving them block (at least with a shield equipped), but this would really just enhance them as raid tanks (where they already shine) and do nothing to address their weaknesses in the other aspects of the game (where they underperform).

What makes Warriors feel weak is their almost total reliance on procs to accomplish anything (i.e. agro, healing, CC). So giving them more options in that regard would help them a lot. You could add in a couple of extra special attacks that would share a single timer (like Monk special attacks):

Hamstring - applies a 50% snare lasting 10 seconds on a successful attack
Foot Stomp - applies a root lasting 10 seconds on a successful attack

Then give them another ability called Weapon Attunement, which would basically allow them to guarantee a weapon proc on their next successful attack. Should probably be on a 30 second cooldown.

Finally, throw in an innate ability that allows Warriors to heal themselves double from bandages and allows them to innately bind wound up to 75% regardless of BW skill.

The battle bandaging bug fixed them for soloing. Obviously that is no longer a thing.

When Dragons of Norrath expansion came out a dev posted “whoops, bash was meant to generate aggro like spell stun. We now realise it doesn’t, so here is a bunch of new shields designed to fix that”. I reckon fixing bash’s aggro generation would go a long way to fixing warriors for multiplayer uses.

Agreed. If Warriors had a consistent way to generate hate on the fly, they would be much better in standard group content.

Imagine a dps pacing itself and avoiding taking unnecessary hits.
This one wild trick to make healers not hate you…

Give Warriors the Combat Abilities (I.e. their aggro abilities.) from Live that they give them in TLPs off the hop so they're not completely useless

Bam, you just fixed Warriors on p99 for group content.

That's why they include them off the hop. Because they know they're broken early on due to bad design choices.

Every class has its achilles heel. What is broken to some is proper design to others.

Most hps of any class? Check
Best mitigation plus mitigation discs on short cooldown? Check
Aggro issues so they don’t trivialize raid encounters? Check

Also, who cares about group content? Ive probably said it before but grinding exp is easy. Even soloing a warrior to 60 isn’t bad. You group to have fun with others and help classes like warriors. If you need a knight to succeed in the Hole maybe it’s a “you problem”.

If warriors held agro like knights,Knights would be even more useless as tanks
I leveled my warrior mostly in groups and agro was rarely a problem
Let the rogue take a couple hits

Some people do care about group content. People prefer faster leveling experiences to slower leveling experiences generally speaking. Time is the issue, not difficulty. Every class can afk camp an easy single static spawn all the way to 60. That takes much longer time-wise, however. This is why you don't see an overabundance of Rogues trying to solo to 60.

The strengths and weakness of Warriors on P99 will remain as facts, regardless of whether you care about grouping or not.