3 of the strongest heroes in the game, Sedna, Oak, and Erebus, are Generals. QoT, also a general, is very strong if played right.
However, it seems to me, when actually played as generals, they are kind of lackluster except for maybe Oak. But as for Sedna, QoT, and Erebus, they are definitely played better in the Assassin style w/ assassin style gear upgrades and skill trees.
Now, if it were just me who found this to be the case, then I don't there'd be much weight to my opinion. However, the vast majority of people I see, especially the effective players, work these General Demigods as assassins. I just don't see that many players work Yeti's, Shamblers, Nightwalkers, and to a lesser extent spirits into scary builds.
Has anyone ever said, "Oh crap, that Sedna went Yeti's! Run!" I doubt it. In fact I usually go, "Ah...that guy probably doesn't know the true power of how to run a Sedna".
The problems I see are thus (most of these points do not apply as strongly to Oak because he is stronger as a minion based hero (partly because he buffs his army and they buff him, and partly because spirits can fly and so pathing isn't an issue):
1.) Minions are a pain to use because of bad AI and bad pathing. A lot of times they just don't do what you tell them to do or they get hung up on a "corner" some where, spinning in circles. To run minions, you have to babysit them almost constantly. This is less of a problem w/ spirits, because they fly and therefore pathing is not an issue. They are more likely to go where you want them the first time you tell them to. Grats, kudos.. for Oak.../golf clap 
2.) AoE, especially late game when people have nearly unexhaustable mana, makes keeping minions up a chore. All of your careful summoning and positiong of your minions is laid to waste by two clicks. Even when the minions are up, a late game assassin will out dps and outlast a minion based DG, and if not, it's easy to just run away from a minion based general. He gave up alot of his "punishing" talents to build his slow-ass, can't path for a damn, army.
3.) It takes way too many skill points and gear items to make a minion based build even reasonably effective or versatile. It just become too huge of an investment when it is so easily countered by AoE or you just become a hero that can be ran away from if the tables aren't favorable for your opponent at the moment. You lose out on some critical PvP talent points if you spend enough on your army to make them useful.
4.) Minions move way too slowly if there is any degree of lag in the game. I don't know why this is the case but what use are my Yetis if they are trailing me by 20 yards half the time? I guess I could just resummon at the point of battle but why should I have to? Shouldn't summons just keep up the pace in the first place?
5.) Summons/minions just seem to do too little damage unless totally buffed out and even then it seems a bit lackluster. There's no burst damage and any steady pressure dps from your army can be avoided by running away until your AoE cooldowns are over.
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With all that said, I can say I had some success w/ minions as Oak. Here's how:
1.) When you have 7 to 10 buffed spirits up, they are great at taking towers down all on their own, even behind enemy lines. You can cap a flag on one part of the map and take a tower down in another. Very nice.
2.) Spirits regenerate themselves automatically, just keep wards down wherever creeps fight each other. Whiz bang...near constant supply of spirits.
3.) A pack of spirits make great harrassers for the more frail gods or those that haven't went aoe. Just send the spirits at them as a constant dot. You can make new spirits almost as fast as they kill them. This is great for forcing certain heroes to retreat to their towers. It also prevents the run and Heart of Life spamming.
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But even so, If I want to be serious about Oak only use spirits as a buff to my dps as I will be rocking penitance, surge of faith and other DG to DG based talents and gear.
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Now, maybe I'm all wrong. Teach me....but you gotta prove it. It would be hard to believe that people are having a lot of success playing Generals as generals when I hardly ever see anyone doing that. Even more rare is seeing anyone doing that with any degree of scary success.
So, Devs, are you happy with the way it is? Are summons and minions supposed to be a novelty or a more integral part of the decision making process when playing the game.
And don't get me wrong, Sedna/Oak/Erebus/QoT are by no means weak. In fact I think Sedna might be the strongest hero in the game. I'm not asking for a Generals buff, but rather a reconsideration of how they are supposed to work.