Are +% haste gear good for dragoon? A lot of the polearms I have found are quite slow? Will the haste help?
Yes.
To give a basic background though, any job that deals damage by whacking things with an object needs haste, regardless of how fast or slow the weapon is. 25% haste (26 due to the way the game mechanics work on haste) is the cap, anything above that amount won't help any more.
So you get to cap and then fill in with other gear. This is overly simplified though, and you will need other information like how to cap accuracy for various mobs, STP to make a hit build, Attack to hit harder, Double, triple and quad attack to hit more times and increase tp gain and many other stats that will help.
But if you have any more detailed questions or any questions about anything ever, this thread is great for it:
http://www.ffxiah.com/forum/topic/29127/random-question-thread-ffxi-related/109/#2099060