Tionese is fine as dps.. Anything above that is a bonus..
For Lost Island you should read the tactics, watch the videos and PLAY NORMAL MODE FIRST..
Once you know ALL the mechanics by heart, then you can try LI HM..
I wouldn't try this as full Tionese unless you're really confident that you know your class and how to really max out damage for your spec. Gear is only half the story and I've seen two Columi/Rakata geared DPS reach enrage on the droid.
Some groups won't care but I wouldn't be surprised to see some attitude about your gear if you're full Tionese. A lot of people in there are well-geared and only go for the Rakghoul Weekly. Though they're the perfect people to 'carry' a Sent who only just meets the gear requirements, not many in this game are very charitable.
For pugging I'd recommend a mix of Columi and Tionese (and likely a piece of BH gear that you'd probably have been able to buy at that point). This gives you some leeway cranking out perfect DPS, a nicer health pool for your healer (particularly as melee), and less aggression from the pugs. And if someone still hassles you don't be shy to mention that the instance drops Columi because it's tuned for people still gearing in Columi. Just saying that and acting like you know what you're doing goes a ways.