Black Garden:
Overall a decent map, especially at low levels. At higher levels it's just a smashfest. If you don't have healers, you lose. I think the fang should do significantly more damage the further you take from the center. Getting a group that hides the fang by their spawn area is miserable. Another option would be to significantly increase the bonus when carrying the fang in the middle.

Codex:
Good balance, nice size, good length / time.

Whitefall Steppes:
Awful. Painful. Its like trying to roll a tennis ball across a football field, with your nose. Yes, you can get from one side of the field to the other, but it's going to be a miserable experience.

Library:
This is okay. Basically the equivalent of throwing 100 ping-pong balls into an empty swimming pool and guessing which one will stop bouncing first.

Port Scion:
Several objectives, variety, and the need for teamwork. Everyone can be valuable if placed properly, even under-geared players. It can take a bit too long sometimes when the bridge is continually contested. The nearly essential need for control of the bridge is a little frustrating, but overall a great map. This kind of resembles DoTA, which is probably why I like it the most.

Now for My Option:

DoTA is still a viable PVP game, even after nearly 10 years of play. If Trion could make a Rift styled version of DoTA, they would be set. Incorporate regular mobs, make multiple, viable strategies for winning available and create small obtainable objectives throughout the game. Maybe even offer a mini (temporary) leveling option during the PVP match.

Another idea would be to create a PVP match which starts everyone at the same level: I.E. - no gear. You keep your level, but obtain gear during the PVP match (much like DoTA) by reaching objectives and killing mobs and players. Currently you can't compete at the same level as other players until you have all the best gear and you can't get all the best gear until you grudgingly crawl through dozens of WF to obtain the best gear. Once you get all the gear, you dominate the WF and it's not as much fun to play them!