I think that in order to make a good build for your class you really need to find which attributes you need to boost and which can be a dump stat. Don't use experiences from PnP D&D or other D&D games.
ALL classes need to get a decent constitution. I think no classes should start with lower than 14 con. Some races and classes should start with 16 or maybe even 18.
Strength is another stat to keep at least at 10. Quite a lot higher if you intend to do some melee. I don't think strength is a dump stat because it depends on how much you can carry. Even wizards need to carry their gear.
Melee classes should try to boost their strength as much as possible. Clerics can get away with strength in the 10-14 range before getting boosts from items.
Charisma is a dump stat for all classes who don't need charisma (paladin, sorcerer, favored soul, cleric, bard). I don't boost cha to the top as a paladin because str and con are more important. With boosts from items and tomes you get high enough. Starting with around 14 cha for a paladin seems right. Clerics can start with 10-14 dependent of the build. If you want to turn undead well you probably should start with 14. Favored soul can start with decent cha for mana, but wisdom is actually more important for difficulty for monsters to resist the spells. Sorcerers and bards need a high charisma.
Dexterity is often a dump stat unless you need it for feats, skills etc. Some classes like rogues need a high dexterity.
Wisdom is another typical dump stat unless you're a monk, cleric or favored soul. Even paladins can use wisdom as a dump stat. They only need to get to wis 14 after items. A +6 wis item means you can start with 8 wis and still be able to cast level 4 spells. Warforged can even start with 6 wisdom and get 14 wisdom with a +2 wis tome.
To make a good build you define which stats you want to max out and go for them. If you try to have a decent score in all stats you will not excel in anything and the build will suffer.
I think most melees only add strength every 4th level. Every +2 strength you get means +1 to hit and +1 to damage. Those add up with enhancements as well. Expect to see fighters with 40+ strength at level 20.
I think putting points in the prime stat only is the way to go in most cases. If you end up at level 20 with an odd number stats you can boost them to even with epic gear (from commendations) or epic enhancements.