Surely its not that hard to stack some lightning and fire? 48 comes from lvl 8 nat res (5 +3) lets say 25/ ring = 50, gs is 35, and boots around 35 & 20 from amulet without fire/lightning stack = 198. This should be enough for travi. If u still feel vulnerable u can stick 2 more points into nat res and not brake the build (yealds 5 res, but it could be the deciding factor).
If u want lazy trav runs u should aim for 16ll or more. This is not very hard to achive. E.g. my ****ty 260 trav mart has 11 ll (socked PS) and one of the rings has 5 ll.
I think 20 is overkill, but it would surely keep u more safe and is not that hard achive. Just sacrify some eg. until u find/ trade for kicky ar ll res eg. ring(or gamble your own). Its true that sometimes u can still die in travi (this is the reason why HC 2 h gfers are pretty rare or dead ), but after 80 lvl its really not very common (in 1 ppl games atleast).
I think Orphan once explained that council is hardcoded for lvl 78 and thus is able to drop 200 ed marts etc. I don't know, if its for all council members or just the named ones. Still IIRC i have not found 180+ ed marts, execs or bh from travi -> Maybe Orphan still lurks here and can verify their mlvl.
And ofcourse u sometimes have to pot in travi