I don't use a HLT, and I just started AG brewing. I don't have a HLT mostly because I would rather brew at the moment rather than invest in even more equipment. Here's my setup for mashing:
10 gal Mash Tun
10.5 gal brew kettle
5 gal "HLT" (My old brew pot)
Tupperware lid
2qt pitcher
In the 10.5 gal kettle, I prepare my strike water. After dough in, I use the 5 gal pot to heat my sparge water. After fist runnings, I drain the mash tun into the 10.5 brew kettle, while fly sparging water from the 5 gal pot into the tun (with the pitcher pouring over the tupperware lid, as to not disturb the grain bed).
Is this perfect? No. I have only brewed one AG batch so far, and I had to return the sparge water to the burner to bring the water back to temp. A HLT would correct this and keep a stable temp.
Hope this helps.