For lazy folks who just want the short version read the bold. ^_^
Ok, I think I'm one of the senior D/War's in the game. For any DPSer the reason they love D/War is your patk/dmg buff. This buff is unparalleled in the game and lasts for 30 minutes. It is much better than priests' amp attack buff and it is one truly great benefit that can get you into parties once a server learns about it.
The ironic thing, yes I said server, is that nobody knows about it because there are so few druid/warriors in the game. Currently the main reason to choose the D/War combo is their ability to cast two group heals instantly. It's not just that d/war has two group heals, but that they can be cast in motion, while you are running and one of them is a raid heal -that is it can hit 12 people not just 6. If geared properly, the D/War is the best group healer in the game -it's not even close.
That said, there are A LOT of reasons why you might not want to play the best group healer in the game. Just think back to the days of the Sega Saturn (the what???)... This was a FAR SUPERIOR piece of hardware to the Sony Playstation, but what the Saturn had on paper never really mattered because the games produced for it were not that good. That is a good way to think of the D/War.
D/War is a great class on paper, but there are a lot of problems when gearing it. Currently in the state of RoM there are absolutely no cloth sets for DPS. This means that you cannot play D/War for endgame DPS -that is lvl 55 and up (probably earlier than that honestly)- and expect people not to laugh at you and kick you from party. While most of the D/War elites focus on melee attacks, the druid main class does not allow ALMOST any gear to make this possible. While D/War is able to wield axes, there are practically no axes with healing bonuses that would allow you to DPS and heal. There is one in Varanas Nightmare, but that is very hard to get and I don't know about you, but I'm not designing an entire build around a weapon I may not even be able to get. If you do some experimenting, you will see pretty quickly that the cap you hit for patk based on stats alone, unbuffed, will be around 50k. (No flaming required if I'm wrong, this is just an estimate). This is because you can't wear leather, and you want a weapon that will not totally nerf your heals. While it is possible to make a D/war that can hit fairly hard, your crit rate will be GARBAGE compared to EVERY OTHER DPSer in the game. Seriously. No leather = no crit. I know, you're saying "But I have accessories and an arena cape!" No man, just no, don't waste your time.
Currently I am a level 66/52/?? Druid/Warrior/Scout. I really enjoy playing the D/War and the rebalancing in Ch 4 may have benefited D/War more than any other class in game. The reason I say that is that we are now able to cast a group heal every 2 seconds. This allows for a totally different strategy to healing than has ever been possible with a druid. Previously the cool downs for each heal was 5 seconds and you need a lot more NP (if you're reading the druid forum you better know what NP is =p). Now, if you are geared well enough, you don't need NP at all. Previously the HoT spells were the bread and butter of every druid healer, but now the d/war is able to effectively heal using only group heal. BUT! Don't be a priest! If you do roll D/War learn how and when to use your other healing spells in combination with the double group heals.
I think I'll let this go for now. I am thinking hard about writing an updated druid/warrior guide, but it will take some time and I want to learn more of the strategies for Temple/Tomb/Grafu/Sardo before I come shooting my mouth off. It has been said before, but I'll say it one more time: PLEASE do not try to make your D/War a melee class. I know it is deceiving, but it is just an illusion. Your druid will never do DPS and that is ok, because within your powers are the best group heal combo spells and the best patk/dmg buff in the game. Even without NP problems it is still a very hard combo to play. Read Xerise's encyclopedia -it's close to the druid bible. Good luck to all you young druids out there and make sure you have fun along the way.