Isle of Conquest really doesn't come as a surprise though since the Alliance has a shorter route to the docks. But that it's actually 80/20 in Altarec Valley I would never have expected.
Well, in IoC you can still hit the guy capping before he gets it off. I think the issue on horde is that there is a big disagreement in tactics. 50% of horde are stupid and go for WS to kill ~5-10 alliance. Around 40% go to hangar (sometimes more though), which is smart and can actually have a decent win rate. 10% and others will go die somewhere else, e.g. docks. Horde rely on the few stealthies we have to kill glaives, which sadly only works around 1 in 5 times. As the expansion carried on, glaives became a little easier to kill, but we still manage to fail before they get it.
And then too few people concern over quarry and the refinery (or w/e they're called), because no one likes to stand there. This kinda happens on both sides--but it can drastically speed up glaives damage--or it can drastically increase the bombing.
Sadly, the hangar tactic is constantly countered by a bunch of allies camping their own base, and then allies just catapult themselves into horde base and start bombing themselves.
In the end, I think it is more of a mentality thing. IoC seems pretty balanced, and when we have a good team on horde, we can really dominate. But there is a big lack of morale, and way too many bots/idiots/afkers/people who are pvping 'just to pvp dude'.
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Sorry for the rant. It actually isn't THAT bad all the time. During call to arms, horde actually can try. But during all other times, we tend to just roll over. On my rogue (alliance), my ratio for IoC is 42-13 (76%), which is pretty good. I don't remember losing that often. As my lock (horde), it isn't that bad: 39-31 (55%). At least it is a winning rate, but I think I played IoC as him more towards the release of IoC. I really just stopped playing it (excepting during leveling) once blacklisting came out (both horde and ally), otherwise I'm pretty sure it'd be around 20%. So I'm not too surprised by the graph.
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As for AV, as Horde I usually feel like there is a 30% chance of winning. As ally, I feel like there is a 90% chance.
I often blacklist AV too, so my statistics are a little old. As my lock (horde), I have 68-51 (57%). As my rogue (alliance), I have 36-9 (80%). Sadly, these statistics might be a little dated (at least for my lock) since I don't have access to my other characters' armories.
But yeah, I can agree with the trend in general. Alliance are usually all-stars in AV. They have a large defending group, and they get towers early. It is hard to counter because so many horde go to belinda and next to no one goes straight for the end GY/last 2 bunkers. Sometimes we'll have a group that'll defend towers, but it is never enough. Usually if we have defense, we have no offense. And it only takes ~2 towers down before they can easily down drek, so ally just need to turtle around Drek and those two towers.
There are a lot more reasons I'd like to go into, but it is all sort of circular and says generally the same thing.
tl;dr I don't think a terrain change will fix the AV problems (or IoC for that matter). Maybe it'll help, hopefully at least in morale (which is what horde really need), but I have my doubts.