Indeed, if you want to get the most out of the game storywise you should increase your Wisdom, Intelligence and Charisma as early as possible. (I'd go with 18 INT and WIS and the rest in Charisma at character creation).
The mental stats of the Nameless One are very significant for what options are available in dialogue throughout the game, and high Wisdom boosts your XP gain a lot, making you level up faster (XP bonus is not retroactive so you want high WIS early). Once your mental stats are in a good spot you can put more into Constitution which will increase your health pool and make you regen health faster. You can also use tattoos from Fell's parlor to boost stats as needed, once you can afford them.
While this does make you physically weak early on you can get other party members who are good at fighting to do the heavy lifting in combat for you. There is no mandatory combat in the Mortuary aside from killing one zombie for a key in the first room, if you choose your words and actions carefully.
Seek out Mebbeth in Ragpickers Square as soon as you get out of the Mortuary, she can train you to become a Mage. Spell buffs can make up for your physical weakness somewhat. Also getting disabling AoE spells makes taking on groups of enemies much easier early on. Pacify at lvl 1 (puts enemies to sleep) and Horror at lvl 2 (makes them run around like headless chickens) are both good ones that can keep entire groups of foes from fighting back while your frontliners hack them to pieces.
Also pick up Dakkon at the Smoldering Corpse bar ASAP, between him and Morte you should be able to manage most fights without much trouble. When you have 18 INT and 19 WIS you can talk to him about the Unbroken Circle of Zerthimon. With those stats you will be able to unlock and comprehend all 8 circles, which will boost Dakkon's physical stats significantly (and give you some free spells).