Actually, 'deadside' joins let you see the signals square just fine. But if you're doing one, you already know the runway in use. So why do you need a signals square? In fact, apart from non-radio ac, does anyone, honestly, still use those useless things? The only ones I've seen have been rusted solid and beyond repair, let alone fit for use for an aviation purpose.
They have one massive advantage -- generally you join lower than cct height on the deadside (500' vice 800'/1000'), meaning other traffic in the cct is skylined and much more visible, as opposed to trying to pick out traffic on downwind somewhere near the Le Touquet circuit when you're wallowing around in the overhead of Stapleford wondering where the other chap joining at 1000' above the cct (pretty sure that's the CAA 'standard') from the opposite direction is...
And as for the collision risk at 'Initials' (about 2nm on the extended deadside for a light single-type cct) -- that's avoided by having SA on other people joining and sorting your spacing out there, before you get back and cause carnage in the cct itself.
Admittedly this is only any good if you trust people to fly ccts at anything approaching a reasonable size, which might be why they've not caught on amongst a lot of the retired Navigators in the Belgrano...