The problem is that, by default, your computer/tablet requests an IP address via DHCP. This is fine except Vz then insists on using their DNS servers. It appears that their servers are slow and overtaxed, especially on web pages that require multiple DNS lookups to display ads, etc.
On my MacBook Pro, I created a profile for the hotspot. I have other profiles for using wifi at home and also using the mobile internet satellite on my motorcoach, and using any of these - or, worse yet, trying to bastardize one of them for the Thunderbolt - will result in total chaos. Once the profile is created, I deleted every device except WIFI. Next, click on the Advanced tab, then TCP/IP and confingure ipv4 manually. Choose an IP address within the range of your hotspot. Mine starts assigning IP addresses at 192.168.1.10 - 192.168.60. Then, make sure your router address is set to 192.168.1.1. Next, select the DNS tab and input public DNS server addresses. I just used Google - 188.8.131.52 and 184.108.40.206 - and you can add more if you want. Click OK and then Apply, and you are golden. BTW, on the Hotspt on my TB, I left DHCP turned on and this has not caused any problems. I left it this way rather than reconfigure my wireless printer. NOTE - using the VZ DNS server (which is accessed via the router IP address), I could not surf to Google or retrieve my Gmail (both unhosted and hosted accounts). However, I could surf to every other web site that was not tied to Google. Not sure why this is a problem other than possibly a timeout issue.
So far, everything has been working exceptionally well. I need internet access on the road and I am trying to rely solely on Vz rather than also paying my mobile satellite internet provider $80/month. Granted, there are times when I won't have a choice and will have to use satellite due to lack of cell coverage, but I want to use Vz as much as possible.
Other than the method described above, that appears to use a public DNS for the hotspot feature, the only other method that I know of to do this requires rooting of the Thunderbolt. I am not too keen on doing this, and I would need to know of an easy way to get back to factory stock if need be.
The other interesting point is that some people have posted that their hotspot feature is working flawlessly, while I and many others have significant trouble. Hopefully the above information will eliminate your connection problems with the hotspot feature on your TB or other HTC phone.
[Edited to comply with Terms of Service]