I love my danubes ... especially the tractor beams.

While you are correct that Siphons received a cap on what their bottom-line is (like 4-5 months back) you seem to have little idea about how they are working. Their bottom-line is ridiculously low. So instead of just having your engines shut down by a Tractor Beam from Danubes also try having your weapons, shields and auxiliary shut down from the same source. Danubes are laughable by comparison to Siphon Drones.

but can they shut down a ship by themselves, with no other power drain thrown into the mix?

Rock Paper Scissors. There's a counter to almost everything in this game but no 1 build can counter everything at once.

1000 Bazillion Quadrillion % This.

If you consider 15-20 available power to all subsystems locked down then yes. Using Emergency power to 'X' and batteries just makes the next pulse drain more which both helps you and hurts you at the same time. You don't have any engine power so you can't really get away and transferring power to engines is also futile. The bottom-line is set to an such an insanely low amount that you can't fight your way out of a paper bag, heal or have any shield resistance. Also, no one's quite sure how Insulators is resisting the pulses from Siphon Drones or even if it is. It really doesn't matter considering the mechanic under which they function anyway. Considering that most people use DOffs to speed up the recycle time on these pets it's also a continuous drain which makes it worse. The only thing that placing a bottom-line on these pets did was make it so they couldn't completely take your shields offline. Now you have to work for a kill a little bit more but it's not hard given your target has no shield resistance and can't move. It's reasonable to assume that accomplishing all these things with multiple powers might be fair play but to have one pet with the ability to do so much continuously is just absurd.

if all that is happening even with points in power insulators, then yes, they do need either a slight dip in power drained per second, or a cap on how much they can drain

the drones should be effective, but only in conjunction with other power drain powers/consoles/etc..;just slapping them on a carrier that isn't set up for optimal power drain should have barely any effect

you think any of that silly crap the kdf has is stronger then a hold at the right time that you cant escape from? your funny, real funny. a stupidly strong NPC tractor beam in a pvp match is the most deadly thing in the game besides a subnuke, your the noob if you dont know that.

Actually I would like to be able to counter the Danoob shuttles without havng to carry 5 copies of TB protection just to play PvP against pets that are a 1000th the mass of my battle cruiser.

The idea to have the Danoob shuttles only slow a vessel instead of completely trapping a vessel is as fair as putting a drain cap on siphon drones.

The tough part is finding something fair but effective for both.

As Antonsoliries pointed out the shuttles suck because being the dumb AI they are they never stop TBing anything thats a target.

Fixing holds so they take into account the relative sizes of the ships would be a good start.

Reducing the over-reliance on Bonus Defense to stay alive for more than a few seconds would be an even better start.