I'll start by pulling some info from memory-alpha.org:
- Tetryon dual heavy cannons can not be bought from any NPC. (Ship-mounted tetryon weapons afaik are limited to a race called the Nasari. The Voyager encountered them once only. The lack of availability is reasonable.)
- Plasma dual heavy cannons can be bought with normal exploration or pvp tokens. (As far as I know Plasma cannons were the weapon type used by starfleet before phasers were developed. Availability would be reasonable, but the last few hundred years plasma-based weapons weren't very frequent apart from romulan torpedoes, were they?)
- Antiproton dual heavy cannons can be bought for the marks gained by daily missions. (Antiproton based weapons so far were limited to the ship created by a Douwd in an attempt to chase away the Enterprise D. Also the "planet killer" apparently used an antiproton based weapon. Very reasonable to find them readily available for shopping. ^^^^)
- Disruptor dual heavy cannons can be bought with normal exploration or pvp tokens. (Klingons and Romulans use disruptors. It's not unthinkable that the federation has access to the technology.)
- Polaron dual heavy cannons can be bought with normal exploration or pvp tokens. (As far as I know this is the signature weapon of the dominion. Might be available, but the federation did not really have nearly as much time developing something with it as with.... [see next point])
- Phaser dual heavy cannons can not be bought from any NPC. (They are THE signature weapon of starfleet. Pulsed (=cannon) phaser weapons were actually used in TOS times. They are the No. 1 reliable and efficient tech available to the federation. It's only logical they are readily availab........ wait .... ehrm ....... no .......
Or to summarize my post: It is beyond ridiculous, that Phaser dual heavy cannons can not be bought anywhere. We're limited to shooting flashy green and purple stuff until a short while ago used by our current enemies or semi-omnipotent beings from the most remote regions of our galaxy ... just because we can buy these things in the Earth-Station shopping mall as a reward for scouting three asteroids. For phasers we need to gamble on rare drops or buy them for extreme amounts of energy credits.
Well, it's just my oppinion, but I think phasers should definitely be more easily available than the really exotic stuff.
I am in 100% total agreement. The fact that the FEderation can buy Klingon/Romulan weapons, but can not buy their own weapons is rediculous. I dont want disruptors, I want my phaser cannons, phaser turrets, and phaser banks, but I dont want to pay outragous prices on the auction house for em....
The OP is correct. You can't get the Phaser Dual Cannons or the Phaser Dual Heavy Cannons from the PvP or the PvE exploration vendors. The only reason I'm disruptor as a fed is because of this. I think its stupid.