I was in my first couple of serious fights last night and it seemed to me that the offensive capabilities of monsters/NPCs is quite high. I am playing a Champion with heavy armor and a shield and they were not struggling to hit me. Most of them had hunter's mark so the damage was quite high also.
In PF1, it seemed like players tended to ignore minions and punks and headed straight for the boss or most dangerous looking opponent. Usually the riff raff had trouble hitting and doing enough damage to worry about.
Now in PF2, it seems like it is dangerous to leave them active longer than necessary. If you have to spend a long time beating on a boss while the punks are stabbing you in the back successfully, you could be in trouble. Even a goblin warrior level -1 has a better to hit than everyone but a fighter at level 1.
Is it a viable tactic to focus fire the rabble down early to reduce the number of attacks each round and wait to go after the boss until the numbers are more manageable?
I think the most general advice possible is 'actively engage in action denial'. Whether this means kiting slower moving foes, grappling/tripping, using hit and run, or burning down a particular opponent, it will depend on the particular fight, but the general idea of 'don't let them do their first choice use of 3-actions' is paramount. Letting an above-level tanky-boss do strike/strike/raise shield will likely go poorly for you. Letting a caster get a 2-action aoe off, before moving out of range/into cover/etc makes you spend more time getting to them.
CC (crowd control) is still very useful. SLowing the big bad down with Tanglefoot, or liquid ace bombs, while everyon plays keep away while taking out the mooks is quite a valid optiono IMO.
The most success ful combats I've had usually ended up with "follks who do damage" and "folks who deny enemy actions or otherwise debuff"
Set 'em up, take 'em down.
That is one reason I enjoy Alch lv 7+ with Pathfinde Agent and Ranger dips, with BottleLightning and Liquid Ice bombs. Every round he's providing a debuff, or a slow down on enemies, Or he's providing an Aid Action to help an ally trip an enemy, or crit succeed a disarm.
On bigger guys first round he acid flasks or tanglefoots (or both if I"m feeling froggy and the situation is decent--Alch'sr eally suck at hitting), so the enemy is slowed, DOTed, and has to spend their actions removing the effects whilet he team scatters and preps or takes out the side enemies.
Generally speaking... you probably want to find a way to put the enemy onto the floor. Tripping is widely available for anyone with athletics, and assurance makes it so that you can very likely auto trip minions that are below your level.
This is a great advantage for a paladin because they have attacks of opportunity as one of their potential feats. Deny the enemy actions, while effectively adding in one more full bonus, crit worthy attack per turn. What is not to love?
There are a ton of other builds you can go for, and this doesn't really touch on larger tactical decision... but it is a nice bread and butter.
I agree with Puksone in that we could use a bit more information about the encounter to comment to your specific experience but here's my 2 cents:
Also I have noticed that when creating a combat encounter 'by the book' the lower floor of mooks is higher in beginning. If that is by design or just happenstance I don't know but as you near level 5 you 'should' start seeing mooks being less and less effective. when building an encounter you can go as far down as party level -4 to fill out the rank and file. The lowest level creature I've seen are -1 so at first level you are limited to fighting at least a 'lackey' class opponent vs low-mid power lackey and low power lackey. So at least at first blush you do have to do a little character growth before you start to really feel the hero vibes but you should get their.
It has been my understanding that at the very bottom of the scale, they chose to make level -1 monsters hit about as much as level 0 monster, but do less damage and be easier to kill.
In addition, a Strength-based character might not quite be at their optimal AC yet. The equipment chapter suggests that Champions start with Hide, for +3 AC with a max Dex of +2. Assuming they're eyeing Full Plate eventually, they might not have a Dexterity bonus, which will give them a starting AC of 16. If they could afford proper armor, they would instead have 19 (prof +3, item +6).
That said, the whole point of minions is that they're dangerous enough that you can't ignore them and focus on the boss.
Mostly Depends on how your DM plays.
You can set up a formation which gives advantages, but it all Depends on how much intelligence your DM wants to give to the enemies.
Will all enemies focus 1, or they all hot different targets?
Will they try to finish grounded character, knowing the fact that magic exists and which means heals, options and so on, or will they move on to targets alive?
Do the enemies have ears?
Or they will not come to help friends even if you are fighting in an adiacente room, just because you are low hp and the party could wipe?
Will you be able to literaly spam rests during an expedition and be always full after each fight?
This is more or Less what could happen or not.
Obviously as said at the beginning, you can try to mitigate the fight you are into, but most of the outcome is up to the DM.
All of this to say that it does not really matter if a fighter goblin lvl -1 has more attack ratio than you, if there is no chance that the party could die.