You don’t need the UK tac in Tobruk to still have decent odds.
Alexandria -> Tobruk (2x inf, 1x art, 1x tank)
Egypt -> TT -> Tobruk (1x inf, 1x art)
Egypt -> Tobruk (1x mech)
65% odds to win, 4% chance for everyone dead, so 69%, let’s say 70%, chance to have it go in your favor. The point is you want those guys dead, because Italy can never reasonably afford to replace them. You can. From South Africa, from India, whatever.
Once those Italians are dead, and once 2/3 Italian transports are dead, a bit of reinforcing Egypt is more than enough to hold it against all practical threats. If you build an mIC there on UK2 (or if you’re overly ballsy, UK1), you’re pretty much good to go if you take your Maltese air left from Taranto and stick it on Egypt on UK2.
If you get boned on dice in Tobruk… and that’s a 31% chance… then… well that’s not good. The Allies don’t win by not taking chances, however.
The tac makes it 92% odds (1% draw), so yeah, that’s strictly better. But to do that, you need to send fighters off of London down to Taranto. That’s risky for all the reasons you’re already thinking.
The Italian dest/TT in SZ 96 is easily killed by your Cruiser in 91 + the fighter on Gibraltar. If you’re unlucky, and the Cruiser in 91 was killed by a German sub, then it’s still likely worth sending the Gibraltan fighter to try and get the job done by itself, though I don’t know if I’d also try Tobruk in this instance. CR+FT vs. DD is a ~2% chance to get screwed. FT vs. DD is a 25% chance to lose. A 25% chance to fail the amphibious assault mixed with the inherent 31% fail chance on the Tobruk fight as posted above ends up being something like a 43% chance to lose horribly in Tobruk if you don’t bring both the cruiser and fighter to SZ 96. (You still have a small chance to win without the amphibious assault, and that’s included ion the 43%.) That’s a bit too risky for my blood.
How aggressive you can be on UK1 depends entirely on Germany’s buy. If you see G1 inf/art purchases, freakin’ go for it. If you see something that is a bit more scary for UK, then not taking that 69/31 chance on Tobruk is something I couldn’t fault you for.