Aelcar did make a point I feel should be emphasised:
Aelcar wrote:It's just that I consider wanting to take something away from someone else without valid reasons a baffling attitude, even more so when this is one of the few classes which are NOOB-friendly and can hit top performance levels without much money or equipment.
Underlined section by me, which may explain some of the misgivings about Favoured Soul. It's a class that can perform in the top tier with minimal investment compared to other builds in that tier.
The class is very newbie-friendly,
especially in BG. Favoured Soul has a nice balance of abilities and feats that help pad the room for someone new to the game, gives enough martial power (WF/S, DR) to still be workable even with poor investment in spells (which a new player is certain to do), and provides newbies an avenue to perform high-level content with not as much need for a bankroll and epic gear as other and more powerful builds would. I think Obsidian may have introduced it in the OC to give an "easy mode" for players new to the rules to get a feel without dying or feeling useless all the time, and likewise its popularity in BG may also be this. Basically, you have to work to make the class unviable; as in "Favoured Soul of Mystra who specializes in shurikens" unviable, which is still "meh, it still works".
Favoured Soul also lacks much in noticeable drawbacks. Gishes and bards work their builds around getting their protection and mitigating arcane spell failure, while Favoured Souls, and by extension divine casters, don't suffer as much; as long as they have the proficiency to wear the armour and shield they want to wear, they can wear and cast without problems. Other specialized builds usually have at least one weak save to need to pad or mitigate in some manner (even
Karond's Dwarven Defender lacks in Reflex that he mitigates with Spellcraft+Evasion+high HP) while a Favoured Soul's saves are high across the board, reducing the need for mitigation, and making mitigation done anyway more effective. The only real weakness I see of FvS is their reliance on buffs--especially the round/level buffs--to be truly devastating, but duration is not as big a quibble as it would be on a cleric due to a Favoured Soul's spontaneous spellcasting mechanics potentially giving more room to refresh these spells should the need arise. And if you're in a tight spot and need to buff, there's always that Greater Sanctuary+Buff combo.
I agree that there are builds that do their roles better than a Favoured Soul. But mechanically, a Favoured Soul is a jack-of-all-trades done right, having the versatility to tackle a significant number of roles adequately, and is very friendly towards newbies or the mechanically inept to boot. But just because I described it that way doesn't really make it okay in BG's context.
Whatever arguments you can make that Favoured Soul is fine as-is and that there are worse builds to look at, I guarantee that if the class had not existed before and somebody tried to get it introduced today, it would either end with the proposal being rejected or the class downsized significantly before being passed. However way it's sliced, it seems that most of the arguments to not change the class boil down to inertia: It's been around for years, people have invested time, effort, and RP into their Favoured Souls, and that there are more powerful builds that do a Favoured Soul's job better...long story short, "It didn't hurt having the class exist up to now; it can't hurt to keep it as-is for a while to go yet".
Truth be told, inertia is an understandable argument, and like the "free doughnuts" issue Valve had when they introduced monetized game mods, nerfing or removing Favoured Souls would undoubtedly cause some grief, and you're already used to the grief you got for keeping it, and better the devil you know and all that.
Since QC has already said they're putting a poll on it, I'll shut up now, but those are my thoughts on the table.
/nickel