Tried it on my extended Legends Vacation in some light PvM. Liked the combo better than mare/beetle in some situations, the tiger while lacking mage has more HP and and better phys resist. Things I tried the combo with: Dread Pirates took them down fast, Serpantine Dragons took them down very fast but required constant healing of the tiger due to crap fire resist, Ishl Titans (Paragon and plain) and cyclopean warriors chewed both paragon and plain flavors up very very fast. Didn't do anything too difficult . GDs did destroy the tiger fast

Regular Dragons did as well. Will use the combo in the future primarily for farming Titan Paragon chest and doing dread pirates. Template I run for that tamer is 120 tame, lore and vet, 120 arch, 120 tactics, 80 bushi, 40 chiv (jeweled to 70) use a comp bow with 50hld, 40ssi, 50DI 40 velocity and balanced. Run a 70s studded suit with 60 MI, 40 stam increase and 12 MR and +9 to dex, +7 to str, and +10 to int. (Cobbled together major and legendary suit) Jewels are 2/6 with 30 dci and hci and crammed 30 chiv into them. So adding me into the mix healing and plinking using Armor Ignore and the HLD it is a solid PvM set up with the tiger/beetle combo. Would probably be a decent PvP set up if I was any good at PvP. Also wear the VvV crimmy, and EP and boots of escaping. Obviously if I ran this template on Siege my gear set up would be a lot more junky

But I believe it would still be a solid 3 way combo, that would deal A Lot of damage fast.
Biggest drawbacks: A lot of walking a garg tamer would be better with the flying at mounted speeds. Tigers fire resist sucks across the board and other resist are low to marginal (Except Phys most I have tamed have between 65-75 phys)
Overall it looks like a decent combo for certain critters. I was going to try it on the Rat spawn but never got around to it, should be effective there though. Would not use it for anything that has primarily fire damage. The tiger not being a mount hurts the a lot IMO unless you want to be flappy winged, open mouth drooling garg

Could be a effective PvP combo from what I see but that is far from my area of knowledge of what is good and what is not. I really really dislike the no mount with this combo as I have no interest in being a garg thrower, just to be able to move at mounted speed, so will continue using the mare/beetle combo for the majority of things.
Disclaimer, this has just been my experience and my opinions formed based on using this combo for a few days.