If your issue appeared with 10.10.3, I am 98% certain it is a bug in OS X Yosemite, introduced with the 10.10.3 update and related to Intel HD 4000 GPUs. Welcome aboard. The kernel panics are totally erratic, some users have also graphics glitches like you describe. The only common feature is having an Intel HD 4000 GPU.

However, your case seems more severe than that and could also be caused by a dying GPU.

On MacBook Pros with dual GPU you can avoid the problem by disabling Automatic Graphics Switching (System Preferences > Energy Saver).

Please contribute to the thread in the apple discussion forum and file a bug report (with link to the thread).

This is not an answer but a list of elements to progress toward an answer.

Kernel extensions upgrade

On the MacOS version having this kernel bug, the Thunderbolt kernel extensions were:

com.apple.driver.AppleThunderboltDPAdapterFamily    5.0.2
com.apple.driver.AppleThunderboltDPInAdapter    5.0.2
com.apple.driver.AppleThunderboltIP 3.1.0
com.apple.driver.AppleThunderboltNHI    4.5.6
com.apple.driver.AppleThunderboltPCIDownAdapter 2.1.3
com.apple.iokit.IOThunderboltFamily 6.5.8

obtained from a grep Thunder | sort on the system report of the question.

On a MacOS version 10.13.5, this set of kernel extensions is:

com.apple.driver.AppleThunderboltDPAdapterFamily 5.5.4
com.apple.driver.AppleThunderboltDPInAdapter 5.5.4
com.apple.driver.AppleThunderboltIP 3.1.1
com.apple.driver.AppleThunderboltNHI 4.7.2
com.apple.driver.AppleThunderboltPCIDownAdapter 2.1.3
com.apple.iokit.IOThunderboltFamily 6.7.8

obtained with the command:

kextstat -a | grep Thunder |
sed 's,^.* \(com[^ ]*\) (\([^)]*\).*$,\1 \2,' | sort

By comparing these 2 sets of kernel extensions one can see that Apple upgraded 5 of these 6 extensions. Maybe this could be to try to fix known bugs and not only to add some new sexy functions.

I would suggest to test this version of 10.13.5 of MacOS.

Reduce the potential source of kernel panic

Since Thunderbolt is used within the stupid network configuration named Automatic, I would test inactivating it if it isn't necessary. This can be achieved in System Preferences > Network:

Create a new location without Thunderbolt

Within Location: select Edit Locations… click on the down left + to create a new "location" (the correct term would be a network configuration):

Wi-Fi ON        Thunderbolt OFF

Select the Thunderbolt Bridge interface in the left list of network interfaces and:

1. Set Configure IPv4: to Off
2. From the bottom left gearing drop down menu Select Make Service Inactive
3. and finally Apply this new network configuration

If with this new configuration, the panics disappear, then this would mean that the IP Thunderbolt driver is where the bug stands. This might be a good workaround to return to a normal working system. This might also be an helpful information to transmit to Apple to help them improve their quality control.