Heavy steering is very subjective, my 1999 +8 with rack and pinion steering and 205/60 x 15 tyres is much lighter than my +4 with steering box and 195/60 x 15 tyres.
The +8 is certainly a heavier car, and therefore the handling is more "ponderous" , if you want "nippy" go for a 4/4 , especially a Sport on narrow tyres.
The back axle with LSD does take some familiarisation , when it breaks away both rear wheels may be spinning rather than just the inside one, so you have to be quite adept at catching it . However if you have got to this point on a public road, you are probably going a mite too fast for the conditions.
I have always maintained that the +8 is more tricky to handle ON THE LIMIT than any 4/4, +4 , or Roadster. That tremendous low down torque that characterises the Rover V8 power delivery which makes the car so enjoyable to drive on a dry road with bags of grip , can turn very interesting in wet or slippery conditions.
In summary , driven sensibly in normal conditions, the +8 is as delightful a handler as any other Morgan , with the added benefit of that wonderful torquey engine propelling you effortlessly at the next bend in double quick time. If you want to explore the limits of adhesion you will find it more of a handful than other trad Morgans.
Andy