Jonesy89: Tying this back to OP, the quests are needed, as others have mentioned. If you don't do them, it will make things more difficult for you.
No. just no.
I played BG1 (actually BGT, but I stopped when the second one started) to completion, for my first time, a few days ago (take or give some).
I also got bored from the sidequests soon, so for the most part, I stuck to the main quest.
there was ONLY ONE time when I had to grind (... do side quests), and that was before the battle on the iron throne building. I did maybe 3 or 4 side quests, following a walkthrough. I gained perhaps 1 level with that, and not for my 6 characters.
I had no problem in finishing the game (even the final battle), although
I was far from the level cap (my party was between levels 6 and 8, I think.) My main character was a pure mage, btw, and since I was using BGT; I couldn't do the monsterspam trick to beat the final boss.
all of that in normal difficulty.
although I have to admit I had to google for help both in the iron throne battle and the final one. (and for the former, I only found that "it was very difficult, and you better use some spells")
TL;DR:
side quests do help, but they are not actually essential. and yes, I also like to stick to the main quest. sometimes.