I've put about 4,000 miles hiking on an ultralight silnylon tent, including Australian and US desert hiking, and many weeks at altitude in the snow. Its been exposed to considerable wear and tear, abrasion etc. It is still going strong - now 10 yrs old - and I'm planning to use it for another backpacking trip this summer.
re wet/dry weight- broadly the thinner the material (and silnylon tends to be very thin) the less scope to absorb water. Even my 10-yr old tent still beads up pretty well, so a couple of shakes and a wipe with a packtowel nearly all the water is gone.
Pack is still a small proportion of my weight - what you REALLY need to do is a get a similarly sized mate to wear your pack, then try and pick them up and imagine carrying all that weight for 20 miles... Whether your tent is wet or dry will, I'll wager, be imperceptible!
I've used a reasonable amount of Decathlon/Quechua stuff, and have also peeked into their R&D/prototyping (but not production) facilities at the big Quechua store in Sallanches, France.
The quality is excellent as is the aftersales. The bladder in my running pack started leaking after a year (about normal for ultramarathon), and they replaced it no questions asked. They didn't have the exact same model in stock, so told me to select whichever bladder I wanted from the shelves and it was mine.
I wouldn't hesitate to buy stuff from them if it was what I wanted. I'm not aware of any large scale gear "manufacturer" (including Alpkit) that doesn't outsource most of its manufacturing, usually to SE Asia.