So let say you were advising a newbie rogue player where to put their second stat (14) after sticking their 15 in Dex. You could advise...
Put it in Con as your character will have more hit points and be more resilient in combat. They will also be better against things like poison traps.
Put it in Int if you want to be an arcane trickster or be good with traps and puzzles. (this is what the PHB suggests)
Put it in Cha if you want to be an infiltrator, good with disguises and impersonation, or information gathering. (this is what the PHB also suggests)
Put it in Wis if you want to be a scout and spot enemies, and detect traps.
Put it in Str if you want to be a swashbuckler type who can swing, climb and swim.
I think all those are valid options but to be honest the Con option is not what I would typically expect in a rogue. I would think given the choice most players would pick one of the other options for their 14 and also their 13 and maybe put the 12 or 10 in Con. I don't think the creator of the pregens has done anyone a disservice with their stat assignments considering they want to emphasis the skill aspect of the rogue class and are also following the PHB advice as well. Sure they might run out of hit points from time to time but they will be slightly better with their core skills every time they roll.
I also think you could apply this logic to most other classes, where Con becomes the 3rd or lower option
That's the worst kind of advice, Prism. You're asking the newb to choose between a number of badly defined "cool concepts" with no basis in the underlying statistics!
You're creating a false dichotomy here Prism, and then you're running with it to set up a conclusion where a 10 Con looks very reasonable if not outright attractive. This completely ignores the real choices.
First off: you can't infiltrate or swashbuckle or detect traps if you're dead.
Secondly: you can still infiltrate and swashbuckle and detect traps even if your bonus is slightly lower than in your scenario.
Thirdly: the PHB advice is consistently awful. It seems to be based more on wishful thinking than actual analysis. That is, its advice is based on "truths" rather than actually reflecting upon the new edition. Simply assuming you need Int for an Arcane Trickster is just lazy. See below for more examples.
You're pitting the abilities against each other like they are equal - they're most certainly not.
But more aggravatingly, you are equating cool character concepts with "14 in that ability". That's misrepresentative and just clumsy.
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What you should do to help a newbie, assuming you are the DM or otherwise have insight in the campaign, is:
* talk to the player and assess whether he or she intends to enter melee much. If "yes", discourage the player from playing a Rogue at all.
* assuming Rogue is still on the table; if the campaign will be challenging combat-wise, advise a +2 CON bonus. It is okay to achieve this by assigning an odd number (that is, the number 13) and then "flipping" it (through racial modifiers or feat ability bonuses etc) - you do not have to start with a 14 before racial/feat mods.
* if the campaign will have a focus elsewhere, and/or the player has some experience with rpgs (including the skill to know when to retreat), you could let him get away with a 12 (or 11, per the above), assuming you leave him with a solid understanding the character is a relatively frail one and should be played accordingly
That is, begin with the end result. Not with the choice.
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Now that you know what CON score to end up with (a 12 or a 14), you can provide solid advice that doesn't force the newb to make choices not well grounded.
Don't ask him or her to choose between being somebody that "spot enemies" and somebody that is "good with traps and puzzles". More importantly, don't set this up as a choice with the implication that if he chooses A he will perform badly at B and C.
First, inform him he will need a good Dex score. This part you actually do and do well by making it non-optional to place his best score in Dex.
Then, you should ask him to assign a decent number to Con. (This is the 11, 12, 13, or 14 numbers game I've talked a little about). Slightly simplified, tell him to put a 14 in Con if he wants to be brawny and sturdy or a 12 otherwise. Tell him he will thank you later (as in ten levels later).
Then and
only then you can ask him what secondary "thing" he wants to be good at. Why? Because now you have taken the basic step towards helping him not to die before getting to do that thing!
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Do note that "spot enemies" isn't primarily about a very high Wisdom. It's about choosing the Perception skill. And, for Rogues, Expertise.
Same with "find traps". As in, exactly the same. Traps is MUCH more about Perception than Int. And again, it's much more about Arcana and Expertise than actual Int.
As for Arcane Trickster - you only need a good spellcasting ability (or Int in this case) if you actually choose spells that force enemies to make saves. If you choose other spells, your Int score
doesn't matter.
I could go on, but I won't. Point is, the connection between ability and end result is much less direct and strong than you make it out to be.
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In the end, you should be careful with presuming which advice is the best, Prism. Other than that, I'll leave you to soak this in.
Have a good day.