I agree and disagree, strongly both ways

It does appear that a point of emphasis for this introduction was not to overpower anything, which really can't be faulted I suppose based upon past experiences.
Imbuing is a wonderful addition, but you don't need a gargoyle for it. My only real "beef" with imbuing is that if you weigh properties going onto an item, you really ought to use the same weights for unraveling. As is, the system itself is disadvantageous.
Mysticim is a nice spell set, compact but decent "range," useful but without anything overpowering. Sure some complained in other threads about cleansing wounds, who probably have observed affects, but not used it themselves, and others complain rising colossus is a bit much, without regard to the very short duration and easy dispel they suffer from. All in all, very well done, yet again you don't need a gargoyle for it.
Throwing, more to your point as it requires a gargoyle character, is currently hard to "love." The drive toward an optimal range is probably a good idea conceptually, but in any form of play other than a group PvM very difficult to attain and maintain against anything more than a mongbat. The limitations need review. I've tried mine in two major variants, as a melee/ range character, and as a caster/ range thrower. I went the latter route first, going with 120 throwing, 120 eval, 120 mysticism, 100 imbuing, 100 tactics, 100 anatomy, 60 chiv + jewelry. You can cast either colossus or animated weapon and begin your tossing, so once you have the optimal range, it’s a little easier to maintain. Where it gets rough is trying to get strength (it takes 140 str to attain max range for weapons, and 120 to lose only one tile), stam/ dex to 120 so you’re not a slow-motion “dexxer,” and if casting is a way of life, as much mana/ int as you can muster. It’s a challenge, even with imbued clothing. There’s also the troubling effect of the DCI penalty, as that mongbat I mentioned earlier hits you every single swing, and the penalty is so excessive I couldn’t find a way to offset it. After noting on UOGuide that you could offset penalties with swords and parry, I tried a different route, where I still am today. 120 throwing, 120 swords, 120 parry, 100 tact, 100 anat, 100 heal, 60 chiv + jewelry. The range penalties suddenly weren’t “as” bad, I could manage stat requirements, and playing the character had a “better feel” to it. But again there’s a major downside, even with 120 parry, you cannot parry a single incoming blow, and the DCI problems are still overwhelming. It can be fixed, I’d recommend maintaining the concept of an optimal range in a lesser penalized method and would maintain the current str requirements, but would lower significantly the DCI penalty and enable parry to actually parry if the skill is present. As it stands now, throwing and the gargoyle requirement associated to it so far as I can tell is a failure. I worked the character hard for a month, but the poor guy is probably forever retired unless something significant changes.
As for gargoyle only items, it seems to me somebody did a pretty good job of working the spreadsheet for the items to ensure both balance and desirability, when taken as a whole and assuming we’ve seen at least most of what’s out there for now. The troubles in my mind are twofold, first you can make a pretty good gargoyle character, you just can’t make one that “rocks.” So the question for a player becomes, why change from a character who can rock to one who can’t. Second, while I can get decent gear for my three gargoyles, the only thing I can’t get close to is “luck,” that pesky little thing required to attain relic frags. I’d add a fancy gargoyle robe in a hurry, with 300 luck, HPR 2, HPI 5, and DCI 5. Whatever they do, something with lots of luck is needed ASAP, and if the item doesn’t really “rock,” well, an otherwise great publish may get reviewed and accepted as mediocre (client aside).
I made 3 gargoyles, and really like the mystic/ imbuer/ mage. Factually as is though, it would have been even better off left as an elf based on items. My thrower is already quasi-retired, and the threads in the warrior forums here indicate nobody is very enthused or optimistic about them. The third was a tamer who I’m reasonably satisfied with, it is nice to be able to move quicker via flying with a greater in tow, but the luck limiting factor (he is stuck literally 1000 points below one of his human counterparts). But let’s face it, having a gargoyle flying tamer, the only character I’ve been able to determine has any advantage whatsoever over the other two races, really shouldn’t be all a new race is about!