Just because two herbs cost the same, that does not equate to them being equal. Unless you made the hose for the DBV longer that how it came than that is not really a factor. Their is more to herb than price, appearance, chemicals and whatnot and when you add in marketing the "price" of things can get rather flexible.
Also, I disagree with the vapor to air ratio. While I do agree vapor to air ratio are important when looking for an impact hit but that is not the whole story.
For example: I have taken a small bag with same amount of herb and felt the same off a larger bag with the same amount of herb. The larger bag is simply diluted vapor but the entire product gets into you.
In my opinion they both lead to the same place but different ways to get their. This is typically what I suggest to people who want to use a vape but have overly sensitive lungs where cooling the draws do not help much, (fellow ill people, though I generally recommend eating it for those types of issues). With that said, for my money, its all about power hits. I love using my DBV or Zephyr with a bong. Though Its not uncommon for me to put my DBV wand on the Zephyr and and let her rip straight from the wand and tube. Though you have to hold the wand to keep it tight or it will leak a bit.
Their has been much debate on the issue on vapor hits. Some are pro power hits some are more wanting the slower ease into the high kind of draws. Their is not a wholly correct answer but one that fits "your" style and needs will be the best for you I think. My idea of ideal vaping may not that of another persons so no matter how much success I have with my style. I do not extort it as the best way as it is only for now, the best way for me and what I am doing, how others interpret that up to them.
Also, this makes me wonder about the quality of the herb. You stated it cost the same. So am I correct in my understanding that you are not well versed in the qualities and whatnot of the herb? If so, see if you have a jewelers lens or a pocket scope that can see 30x and to 100x is even better. You want to look at the individual heads of the trichromes. You are looking specifically to see if they look "clear" "Cloudy" and "Amber." If you have properly dried and cured herb, most likely more dried than cured, than you want to see about a generic average of 10-20 percent amber trichromes with the rest cloudy and may be a few clear. If you see more clear than anything else it was harvest too soon. If you see more amber or stalks that look bent over with a heads on than its degraded and will be more couch like but still strong.
Think of herb as a fruit. It has to be harvested at specific points of ripeness to better manage certain affects from the herb. It is not common for dispensaries to buy respected names of herb that look beautiful but are not yet prime for harvest. In California, appearance is a higher degree of selling power than in many other places. I recommend before purchasing you actually evaluate it rather than take the bud tenders opinion of it.
If you do not see many trichromes than they may have broken off due to handling, unscrupulous collecting of kief by others before you.
Repeat and stir as applicable. I can get on average depending on size of bowl 10-20 large draws being conservative. For you only to be getting two draws is not anywhere close to normal in my view. Something is not right.
Just gonna go over a simple DBV session to make sure all bases are covered.
Turn on to normal vape range. (once heated, a few minutes)
Fill wand as per regular use, not how you normally do it but fill it as per recommended if needed.
Place wand and draw slow.
remove wand and exhale.
Repeat
Repeat
Stir
Repeat
Repeat
Stir
If you do not make it this far my first place to look is your temp setting. Try turning the temp down a notch when you do another wand and see if that helps. You should far more draw/stir sessions than what I have shown.
Its either the herb, vape or you. I suspect its the herb.
Might also want to look at these vids.
General Vaporizer Information:
http://www.youtube.com/watch?v=_Dtvs8fMxLE
Vaporizers 101:
http://www.youtube.com/watch?v=a9luNVYlT_E