Tele isnt technically necessary for mini's, but for the real deal, its indispensable. You need your minions to tele stack onto the bosses, as well as the fact that you need to be able to keep your summons from spawning the ubers before your ready, which is hard to do without tele.
As for gear, I'm sure you could do it with lower gear, but I never step foot in Uber Trist w/o...
- Hoto (Beast isnt really important here, i'd rather have the resists)
- Enigma
- Shako
- Mara's
- Homunc (Um'ed or P'Diamond'd)
- Arach
- High NTorch
- Anni
- 5+ Summon Skillers
Though your merc is a great help, I havn't found him to be necessary, if he dies, dont bother to replace him, that is, unless he's wearing some nice gear like eth coh, eth infinity, and guillaimes/kiras.