Were customs a good idea? Yes and no. Part of the problem with customs is that they outclass -everything- in the game, to the point where there's no reason to -not- have customs.
Unfortunately, to some degree, it seems like the game got balanced around people having customs, rather than considering customs as a nice plus. Obviously, some people *coughenthorcough* will disagree. Customs reach a point that they even make quest gear obsolete, and there's only one reason to get quest gear... okay two. The first is as an intermediary stepping stone toward customs. Usually a weapon for that burst of damage compared to anything else you get low level.
The second is you're playing a character with a self-imposed no custom challenge.
Having customs -is- good, because it allows us to fill in less common armour types that we can't readily get at multiple levels--ignoring the fact that customs outright outpower these with ease.
The next problem ties into resistances, and by extension healshield. Pre-wipe, resistances weren't that big of a deal, they helped. But it was to a point where you could run around with a mix of runic, quest, and maybe a custom here or there and you could reach 180 fine(we were all around the 180-190 range when the pwipe happened). And you could do this any way you wanted. In fact, dual-wielding vampiric weapons was a very effective method of sustain.
Post-wipe, if you don't have resistances, you're nothing more than a glass cannon. Either you burst them in three rounds, or they burst you in three. Adding in brands/opens that were required to make mobiles a threat for customed characters, means that it's stupidly difficult at higher levels to survive without customs. And even with customs, you need healshield on top of that--which makes having a priest around rather redundant(on top of priest's rather lacklustre offensive capability, which is another problem altogether).
So with customs you've pretty much turned them into a need--again, some people will disagree. It -is-- entirely possible to reach level 200 without customs, but you're going to have a lot harder time doing it--rather than a bonus. Factoring in the necessity for resists and healshield just to survive... something changed post-wipe that seemed to focus on how strong customed people were pre-wipe. And you know, fuzzbutt, the reason for the pwipe was partially to re-balance the game because of how strong customs were.
Mage spells are ridiculously powerful without resistances, fighter classes(and augmenting upwards of 10th attack for anyone else) pretty much dominate higher level capability because mana is a finite resource not easily replenished--and has a 20K cap--and because everyone is either resistant to everything, you're either an all-in-burster mage with the ability to destroy one resist and abuse the hell out of it... or you're a defensive tank that can hit one or two resists slightly and then just whittle you down.
Which pretty much makes the "in-betweens" unable to compete in PK. Not that it matters to me, PK is lame.
tl;dr: Customs are far too powerful in compare to standard gear, damage is way too high from mobiles requiring resistances and healshield to survive, mage damage output is stupidly ridiculous, spells are only effective GM'd(seperate issue, sure), giving fighters and those who augment attacks ridiculous staying and offensive power(also, stun completely destroys mages, which means if you augment attacks and barrel, you're practically invincible to spellcasters(and priests just become a non-factor since spellcasting is our defense, we don't have an offense).