I can feel your frustration, and have been following your posts. My Tablo has been disconnecting from my home network almost every day since I got it a month ago, and I've been working, like you, with Tablo support people who tried a lot of things that didn't end up solving the problem. My disconnects happen mostly at night after we're asleep.
There was actually a 4-day period a little over a week ago when there may have been no disconnects, but we were away during that period and not using the Tablo or any of the other devices and computers on the network. I say "may have been" because I left the Tablo in "heartbeat mode" thinking support might want to do some more remote diagnostics, as they had a few days earlier. When I got back home it was no longer in heartbeat mode and was still on the network. Maybe support re-booted it? During the 4 days away my Tablo was running firmware beta 2.2.13, which I volunteered to use. Upon my return it downloaded and installed 2.2.13, I suppose the released version, which it is still using now.
This period of sustained connection started me thinking about possible network interference and the bandwidth my router is able to give the Tablo. My router is a D-Link DIR-825 that is about 5 years old -- same vintage as your router, I believe. Using the inSSIDer 2.1 utility I saw that my router is broadcasting only in channel 1 of its 2.4 GHz band and that my nearby neighbor's network is using only channel 11 (and is down 75 db), so there should be no interference from her network. Neither of us is using any 5 GHz channels.
But why was my network using only channel 1? Then I remembered: Years ago (when I had the same router) I was having problems of getting disconnected from the internet, and thinking it might be interference I changed my router's channel width from Auto 20/40 MHz to 20 MHz. It turned out my disconnects were being caused by an antivirus program, not my router settings. But I forget to change the channel width back to Auto 20/40.
So about 5 days ago I did change back to the Auto 20/40 setting, and inSSIDer shows me the router is now using channels 1 and 5 (the whole 40 MHz bandwidth covered by channels 1-5). Tablo has not disconnected in any of these 5 days. I have been home the whole time (my wife and I are retired) so there has been plenty of activity on the network, with us using 2 computers, internet telephone, Iphones, an Ipad, 3 FireSticks to watch 3 TVs, a Roku-2 (just for watching Netflix and Amazon since before Tablo was born), and of course the Tablo, being used for TV watching and making recordings day and night.
So I'm thinking the problem of Tablo disconnecting may have been (maybe just for me) that it was starved for bandwidth by my older router with non-optimum settings. I'm hoping the problem is now solved, but would not be very surprised if it comes back.
I should add that during these last 5 days I did make one other change to my setup: The TV stations we were watching via Tablo started (during this time period) to sometimes show stutter and dropouts, so I went up to the attic to test the Channel Master low-noise medium-gain preamp connected to my attic CM antenna. I found the CM preamp, only in use for 2 1/2 weeks, had failed (Sad, very Sad...). Removing the preamp eliminated the bad TV picture, and I got the prior good reception as indicated by Tablo's five green dots for all our TV stations. I believe the preamp was working at the start of the 5-day period, so probably it was not the cause of the earlier disconnects -- but maybe the preamp failure was intermittent, who knows?
A few days into this last period, and before I realized my router was providing 20 rather than 40 MHz bandwidth in the 2.4 GHz band (and providing nothing in its 5 GHz band), I decided I needed a more up-to-date router, one with 802.11ac capability. So I ordered the TP-Link Archer C7 Wireless Dual Band Gigabit Router (AC1750). Hey, what's another $90 after the expense of the Tablo, a 2TB WD Elements USB hard drive, a fancy OTA antenna and preamp, and three Amazon-TV FireSticks? I'm discounting my time and aggravation because I'm retired.
The new router arrived yesterday and I'll probably set it up in the next few days. It's 802.11ac capability should give the Tablo a lot more comfort in streaming to our Firesticks over 5 GHz channels (no more disconnects), and I'm hoping our TV viewing interface will be a bit faster. Tablo is such a great concept, and very impressive when it's working. But, as said by my insightful, non-technical wife in commenting on the disconnect problem, it (the Tablo) is faced with "so many pixels and so little time." I say that maybe it would not have problems if it's on a solid, fast, high-bandwidth network.
I'm really glad I kept our Dish Network satellite TV service (with DVR service). It has served as a backup for when the Tablo has disconnected. When we first got Tablo I cancelled our Dish account, but afterwards they called with price offers so low I just couldn't refuse to remain a subscriber. Dlomneck, you have coax connections from your antenna to your TVs as a similar backup, but without DVR capability. I would advise anyone thinking of going OTA via Tablo-DVR to keep their cable or satellite service for at least a month.
I would just add that I think Tablo support has been helpful in solving some earlier, more serious problems. They have always been very prompt in replying to service requests and have always followed up after having me try different procedures. It seems they tried hard to solve my disconnect problem and did not succeed, but if the problem was with my network/router how could they be expected to have succeeded. Although I guess they might have suggested I check my network and router...
Good luck to all who have the Tablo disconnect problem. I'll let you know how I make out using the new router.